Isospora belli infection is the most frequent coccidiosis after cryptosporidiosis in AIDS patients. Chronic watery diarrhea is observed. Trimethoprim-sulfamethoxazole is the recommended treatment. Four AIDS patients were intolerant to this drug and were treated with doxycycline and nifuroxazide. Three patients were cured. Two patients died of other infections. The two last patients relapsed and were treated again with long term doxycycline. No relapse occurred during the following twelve months.