Although Q fever is endemic in the northern coastal part of Croatia, it usually occurs sporadically. Analysis of 58 patients hospitalized for Q fever during the last 10-year period (1989-1998) revealed some differences in the clinical manifestation compared to a previous study (1954-1977). Most cases of Q fever (N = 55; 91%), presented with pneumonia, but no rash was noticed, compared to 46% of patients with Q fever developing exanthema in the previous study. The previously observed high seropositivity to Coxiella burnetii among domestic animals was confirmed in this study. A two-peak seasonal distribution of Q fever observed in 1991 was connected with the imported Russian sort of sheep with special biology of delivery. The clinical outcome was favorable for all patients, since no complications or chronic forms of the disease were recorded. Disproportion between the number of registered and hospitalized patients, including a number of asymptomatic and several undiagnosed or misdiagnosed infections, leads to a conclusion that the real number of persons infected with Coxiella burnetii in the area is several times higher.