The clinical information of acute Q fever in Taiwan was limited. A clinical study of 109 adults with serologically documented acute Q fever in the past decade (1994-2005) at 3 referral hospitals in southern Taiwan was reported. Their clinical manifestations, laboratory findings, and clinical outcomes were analyzed. Males predominated (98, 90%). There is a significant correlation between monthly average temperature and case numbers of acute Q fever (r = 0.74, P = 0.006). Fever (99%), chills (69%), and headache (45%) were the common symptoms, and relative bradycardia (44/60, 73 %) was often noted. Acute hepatitis, defined as either serum aspartate aminotransferase >or=60 IU/L or alanine aminotransferase >or=78 IU/L, was found in 88 (85%) cases, and more than one-third (31/87, 36%) had hyperbilirubinemia (serum total bilirubin >or=1.4 mg/dL) at initial presentation. The intervals between initiation of appropriate therapy to defervescence were longer in patients with hyperbilirubinemia than those without hyperbilirubinemia, irrespective of tetracycline or fluoroquinolone therapy. Of note, 8 (7.3%) cases experienced a prolonged period of fever (>28 days). In southern Taiwan, the predominant presentation of acute Q fever is acute febrile illness with hepatitis with or without jaundice. Acute Q fever should be added to the list of differential diagnoses of patients with fever, headache, relative bradycardia, elevated serum aminotransferase levels, or prolongation of activated partial thromboplastin time, irrespective of jaundice.