Pneumocystis carinii pneumonia is apparently still rare in the United States, since only seven deaths from this cause have been unequivocally proved. The seventh of these cases, from the John Sealy Hospital, Galveston, Texas, brought to our attention this interesting and serious interstitial plasma-cell pneumonia which we had not heretofore recognized. Pneumocystis carinii pneumonia has been known in Europe only in recent years, reaching epidemic proportions in the last decade. It was first described by Ammich (2) in 1938. An increasing number of cases were subsequently reported in Germany and Switzerland, with rapid spread peripherally from these countries into other European areas. In 1955, 1 case was reported from England. Three cases were reported from Canada in 1956 and from 1957 to 1959 there have been reported 1 case from Connecticut (3), 2 from Oklahoma (11), 1 from Georgia (8), 1 from Arizona (5), and 1 from Louisiana (10). The first recognized case in the United States was reported in 1955 (9) a...