The arthritis of rheumatic fever in adults may mimic acute gonococcal arthritis. To further characterize this clinical picture the features of six patients presenting with the migratory polyarthritis of acute rheumatic fever have been analyzed. There were two men and four women, ranging in age from 18 to 43; in five the initial clinical impression was gonococcal arthritis. In all patients, however, the diagnosis of acute rheumatic fever was subsequently established. Characteristics of acute rheumatic fever not commonly described included tenosynovitis in all six and an erythematous rash in three. In three patients synovial fluid WBC exceeded 28,000/cu mm, with greater than 90% neutrophils. In five of the six, gonococcal arthritis was ruled out by appropriate studies and by failure to respond to antibiotics in all patients. The one patient with serum antigonococcal antibodies had gonococcal pharyngitis and acute rheumatic fever.