BACKGROUND Iridocyclitis has been identified as a dosage-dependent side effect in patients with the acquired immunodeficiency syndrome who are treated for Mycobacterium avium complex infections with systemic Rifabutin. We reviewed cases of acute hypopyon uveitis occurring in patients with AIDS to establish whether there was an association or not. METHODS All patients were referred by an infection disease specialty service for complete ophthamological evaluation and ancillary laboratory. Six patients with AIDS, aged from 29 to 65 years, presented with acute unilateral hypopion. RESULTS At the time of presentation, all six patients were receiving treatment for MAC infection with Rifabutin (dosage range, 300-600 mg/d) and four received Fluconazol. Results of microbiological investigations were negative. Hypopyon developed in the second eye of two patients. Hypopion resolved rapidly with intensive antibiotherapy without corticosteroids. CONCLUSIONS Concomitant use of Rifabutin and Fluconazol may precipitate hypopyon uveitis. The cause of the uveitis is less certain, but the possible role of a microbiological agent cannot be ruled out.