The 4077 Mobile Army Surgical Hospital (MASH) is a U.S. Army field hospital located near Ouijongbu. Major areas of the hospital compound include the mess tent, the Officers' Club, the Swamp, the latrine, the hospital tent (which includes the Pre-op Ward, the O.R., and the Post-op Ward), the various nurses' and enlisted tents, the Commander's tent, the V.I.P. tent, the Helicopter pad, and Margaret's tent.

Landmarks around the 4077 include Rosie's Bar and Grill and the minefield.

Commanding officersEdit

• Lt. Col. Henry Braymore Blake (novels, movie, TV series)
• Col. Sherman T. Potter (TV series only)
• Maj. Frank Burns (in the absence of Lt. Col. Blake or Col. Potter) (appeared in novels, movie, and TV series, but only assumed command in TV series)
• Maj. Charles Emerson Winchester, III (in the absence of Col. Potter after replacing Burns) (TV series only)
• Capt. Benjamin Franklin "Hawkeye" Pierce(as Chief Surgeon, during the absence of Col. Potter, while Maj. Winchester was ill or too involved in a case) (TV Series only)