In Korean, there has been an increasing concern on rickettsiosis as a possile common cause of unknown febrile illness since Tsutsugamushi fever among koreans was reported first in 1986. We experienced 10 cases of Tsutsugamushi fever ocurring in the Mokpo area during the period of 3 months (Oct, to Dcc.) in 1990, which were diagnosed clinically and serologically by indirect immunofluorescent antibody test. The following results were obtained. The most frequent symptoms were fever (100%), headache (90%), chill (60%), conjunctival injection, and lymphadenopathy. Common laboratory findings were leukopenia (WBC<5000/mm3 30%), elevated ESR (>20mm/hr, 30%), positive CRP (60%), and elevated Alt/AST. Antibody titers against R. tsutsugamushi ranged from 1:80 to 1:1,280, but they showed no antibody reaction to Hantaan virus and leptospira. All patients showed good response to antibiotic therapy with chloramphenicol.