The only strain of Rickettsia quintana isolated in Africa was found in September 1938 in a healthy carrier who hadlivedf or 2 years in a closed community (interned in a hospital for mental patients) without ever showing any febrile disease. No case of trench fever was reported to have occurred in his environment. Investigations regarding patients in various hospitals in the city of Tunis with histories of recurrent fever have always proved negative. No case of trench was ever observed for the past 22 years in the feeders of the louse colony maintained in the laboratory, which had on several occasions been contaminated with Rickettsia pediculi but was free of infection at the time of isolation of the R. quintana strain and for 12 months thereafter.