We report here 63 sporadic urban cases of acute Q fever diagnosed in 1985-1997. Fifty-eight men and five women were included; the mean age (+/- SD) was 35.6 (+/- 10.2) years. Twenty-six patients had pneumonia, 30 had hepatitis, and 7 had a self-limited febrile illness. The most frequent radiological abnormalities were lobar or segmental alveolar opacities involving right lower lobes. Chronic bronchitis was significantly more frequent among patients with pneumonic Q fever (P = .01). Thirty-two patients' illnesses were diagnosed through seroconversion, 12 by a fourfold increase in serum antibody titer, and 19 by initial high titers. Patients who initially received doxycycline had a significantly shorter duration of fever than those treated with erythromycin or other antibiotics (P = .0001 and P = .0004, respectively). No patient died. Acute Q fever affects mainly urban men, most frequently causing hepatitis, except in those with chronic bronchitis, who more frequently develop pneumonia. Hepatic Q fever presented with more pronounced increases in liver function test values than did pneumonic Q fever. Treatment with doxycycline caused a significant reduction in the duration of fever.