The entrance leads to three labs, each containing one piece of the stealth suit Mk II armor. There is one area that can only be accessed with an upgraded sonic emitter. After the three labs, the Courier will reach the main room with metal walkways. One can then access a doorway on the right that opens to a small virtual reality test room which is no longer functioning.
From that same area, a stairway can be found on the left that goes downstairs to the night stalker test area, which leads to tunnels and the strange still. Alternatively, once all three pieces of the stealth suit have been retrieved, the player character can access the central door by unlocking it via the security terminal to the right, which leads to the X-13 Stealth testing lab section which has two levels. The top-level consists of walkways which function as observation points for researchers above the stealth testing area and the lower level are the test track for the stealth suit Mk II and the associated quest, Project X-13.
- Stealth suit Mk II disassembled into the three pieces (boots, chest plate and gloves) and is automatically added to the inventory, after all, three parts are collected. It has a weight of 25 once assembled.
- Upon entering the facility, go through the first door and go left down the hallway. The rooms before the end of the hallway are labs #1, 2, and 3. One part of the armor is found in each of the lab rooms on identical tables showing an armored man diagram.
- Upgrade information for the K9000 mod - Mentat chow - Stored in office 2's observation area terminal, and a Nuka Cola Victory on a desk next to a hot plate in the same room.
- Upgrade information for the K9000 mod - Resla roil - Stored in the observation area terminal.
- Auto-Doc Upgrade: Implant Y-7 holotape for the Implant Y-7 - Stored in the terminal just left upon entering office observation area #1 (not to be confused with office observation area #2). Office observation area #1 can be found by entering the reception observation area, and going straight to the other side of the room, where there is a door with a sign on the floor reading "office observation area #1."
- X-13 document - In a wall safe in the administrator's office. Shuts down all security measures in the facility.
- VR simulation note - A paper note in the broken VR simulation room next to a skeleton.
- Sonic emitter notice - Found on all terminals in the facility.
- Recipes - Lockpick skill book -Can be found in one of the vents in the stealth testing lab, the one over the double doors in the reception area. It is possible to reach the vent while standing on the railing in the reception observation area.
- Recipes - Sneak skill book - From the test entrance turn right and go through the left door (the one sharing a wall with the "Hold up, Rocketeers!" poster), go through the door just on the right (the one sharing a wall with the REPCONN poster), go through the hole in the wall on the right, go straight through the next hole in the wall, and the skill book is between the two fridges.
- Two Chinese Army: Special Ops Training Manuals - One is in the reward safe upon completion of all the stealth suit tests, and the other is located on the floor in the room where the chest plate for the sneak suit is acquired.
- X-8 kennel key - In a suitcase in a room with a force field covering the door to the right upon entry.
- There are three thick red pastes and two thin red pastes in the room where the prototype boots are located, on a table at the room's south end. This is the only place in the game that thin red paste can be found without the Them's Good Eatin' perk.
- Protonic inversal axe - Found in the hard-locked stealth test area #2 (VR simulation room).
- Two bottles of Nuka-Cola Victory - One is located underneath a chemistry set, on the first floor, before the testing lab, along with a Nuka-Cola Quartz. The other Nuka-Cola Victory is found near a hot plate in office 2's observation area.
- The rare doggie treat can be found in a dog bowl where the night stalkers spawn on the lower level of the main floor.
- Four Battle Brews - Three in a strange cask in the night stalker area of the basement, and one on top of a force field in the ceiling of the same room.
- Three Stealth Boys - One in the Battle Brew room, sitting atop a forcefield in the ceiling that can be disabled with the sonic emitter, one to the right of a terminal with a bottle of wine, above the REPCONN managers office, and one in the research area, on the table immediately to the right of the entrance, on the desk with a terminal and an Irr. Sunset Sars.
- There is a LAER on the roof of the facility which is accessed by walking along the pipe joining the north wall of the building to the small cliff. Start from the Big MT west tunnel's left side, near two duffle bags, and go up.
- Preserved meat - Can be found by following the tunnels in the lower area under the force field on the main floor. The still can also be found in the room.
- Several parts of the Chinese stealth armor can be seen around the facility.
- From the main entrance, downstairs, towards the end of the night stalker test area, there are sewage tunnels that will lead to a crashed room containing a strange still. A note on the still reads, "1 vodka, 1 mutant cave fungus, 1 Salient Green," which is the recipe for the still to make Battle Brew. The room also contains some Battle Brew in the knocked over the refrigerator and a "strange keg" in the corner.
- In the same area as the strange still, if the player character lingers too long, around six invisible night stalkers can spawn in the tunnel and rooms above.
- In the room where the strange still is found, by looking directly up towards the ceiling a force field will be active. With an upgraded sonic beam emitter the Courier can deactivate this field causing a stimpak, super stimpak, one Battle Brew, and several skeletons to drop from the deactivated field above.
- The interior wall vents in the observation areas overlooking the test course are actually containers concealing loot. This includes the vents that cannot be reached from the walkways.
- In office #2's observation area on the wall opposite the entrance is a poster for Love Sets Sail! starring Vera Keyes.
- In the VR room where the protonic inversal axe is found, it is held by a skeleton, with a note explaining why he smashed the console in front of him. It seems the VR room malfunctioned and killed its subjects. However, Psycho can be found nearby a skeleton, implying the user may have gone insane.
- Among and behind the structures to the northeast of the entrance, there are several broc flower and xander root plants.
- The area is a common spot for robo-scorpion spawns.
- Killing the robots inside the Testing Facility, at any point in time, will yield unique commentary whilst wearing the Stealth Suit MK II, like that those robots could have helped in defending the facility or that they were never allowed to do this before.
- The ambient track "Serenity" from Fallout 2 is played within the X-13 research facility.
- Stealth Boy, but the sonic emitter may not disable the stealth field. [verified] The ceiling of the Battle Brew room hides a
- Project X-13 inside the stealth testing lab the player character may find that one of the doorways/entrance ways between the stairwell and the second-floor metal walkways on the observation level may become bugged, whereas the door appears to be open but an invisible barrier prevents the Courier from going through. However, there is another available doorway so the player character can route around the bugged doorway. During the quest