Fifteen consecutive patients with acute arthritis were studied. Careful culture and microscopy of swabs from mucosal sites were performed to examine the hypothesis that the acute tropical polyarthritis commonly seen in Zimbabwe is due to undiagnosed gonococcal infection. Rheumatic fever and Reiter's disease accounted for two cases each. Gram negative intracellular diplococci were found in three patients who would otherwise have been diagnosed as having tropical polyarthritis. Except for two of the remaining eight patients, who had raised anti-streptolysin O titres suggesting recent streptococcal infection, no explanation for the arthritis was found. The clinical entity of tropical polyarthritis may not be due to a single aetiological agent.