A 6-year multicenter therapeutic study was performed on 1100 children with brucellosis in order to compare several antibiotic combinations and duration of treatment. The patients were randomized to receive oral therapy with oxytetracycline, doxycycline, rifampin and trimethoprim-sulfamethoxazole (TMP/SMX) either alone or in combination with each other or combined with streptomycin or gentamicin injections. The patients were also randomized into three groups based on the duration of oral therapy: 500 patients were treated for 3 weeks; 350 for 5 weeks; and 250 for 8 weeks. When intramuscular aminoglycosides were used, streptomycin was given for 2 weeks and gentamicin for 5 days. In oral monotherapy oxytetracycline, doxycycline and rifampin showed comparable results with low relapse rates (less than or equal to 9%) and no statistically significant differences were found among 3-, 5- or 8-week durations of therapy. TMP/SMX alone showed an unacceptably high relapse rate (30%) with all durations of therapy. In combined oral therapy rifampin plus oxytetracycline, rifampin plus TMP/SMX and oxytetracycline plus TMP/SMX showed comparable results with low relapse rates ranging from 4 to 8% in patients receiving therapy for 3 or 5 weeks, no relapses occurred in patients treated for 8 weeks. When oral monotherapy was combined with either streptomycin or gentamicin, very few relapses were seen, irrespective of the duration of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)