The clinical manifestations of 227 cases of Mediterranean spotted fever (Boutonneuse fever) were reviewed, and the epidemiologic aspects of 170 cases from the Valles Occidental region in the county of Barcelona, Spain, were analyzed. In this area an increase in the incidence of the disease has been noticed during the last several years. The patients evaluated presented with high fever and a generalized maculopapular rash. The tache noire at the site of the tick bite was seen in 166 cases (73%). Other common clinical manifestations were myalgia (73%), headache (69%), conjunctivitis (32%), hepatomegaly (44%), and splenomegaly (19%). Hepatic function tests (serum glutamicpyruvictransaminase, serum glutamic-oxaloacetic transaminase) gave abnormal results in 55% of all cases. The Well-Felix reaction waspositivein 79% of the cases; the OX19 strain of Proteus vulgaris was the strain most frequently agglutinated. Treatment with oral oxytetracycline or chloramphenicol was effective in all cases.