A total of 500 subjects (288 males and 212 females) were tested in Addis Ababa, Ethiopia, in Virology and Rickettsiology Division of the National Research Institute of Health, in 1987, for anti R. prowazekii using Complement Fixation Test (CFT). Out of these 58 subjects (41 males and 17 females) were also tested for anti R. typhi using the same test. The study population included three groups. Group I included 200 patients referred to the National Research Institute of Health (NRIH) for the Weil-Felix test for the diagnosis of typhus. Group II consisted of 200 patients with febrile illness visiting the Outpatient Department (OPD) of St. Paul's Hospital. Group III included 100 blood donors' serum samples included from previous collections. The blood donors had no sign of febrile illness during the collection of the blood samples. The results showed that anti R. prowazekii was detected in 38 subjects (7.6%). The sex ratio among the positive subjects indicated that there were 32 males (22%) and 6 females (2.8%). From the 58 subjects who were also tested for anti R-typhi only 7 (5 males and 2 females) (12%) were found to be positive. Only one person was found to be positive both for anti R. prowazekii and anti R-typhi. From 200 samples (Group-I) tested both by the Weil-Felix test and by Complement Fixation Test for anti R. prowazekii only 4 samples were positive by both test, thus showing very low percent agreement.(ABSTRACT TRUNCATED AT 250 WORDS)