The clinical spectrum of rickettsioses in patients admitted to our hospital (Department of Infectious Diseases, General Hospital of Zadar) from 1983 to 1988 has been analysed. This spectrum consisted of the following diseases: murine typhus, Q-fever, boutonneuse fever and Brill-Zinsser disease. The low number of hospitalized patients with rickettsioses was in disproportion with the prevalence of antibodies to these rickettsiae in general population of the Zadar area. Our results indicate that the main reason for this disproportion are misdiagnosed and undiagnosed diseases.