One hundred two children, 45 days to 14 years of age, with proven brucellosis were studied to illustrate the epidemiologic, clinical and laboratory findings and to assess the outcome of antimicrobial therapy. The main source of infection was the consumption of raw milk in 80% of the patients. The predominant presenting symptoms and signs were fever, arthralgia, malaise, weight loss, arthritis, hepatosplenomegaly and lymphadenopathy. Brucella melitensis was isolated from 75% of 87 patients. Diverse hematologic and biochemical abnormalities were found. Different durations and combinations of trimethoprim-sulfamethoxazole or tetracycline plus streptomycin or rifampin were used for therapy. Eight-five patients were followed for an average of 14 months. Twelve (85.7%) of 14 patients treated with two-antibiotic combinations for 3 weeks relapsed, as did 5 (8%) of 62 patients treated for at least 6 weeks (P less than 0.001). No relapses occurred in 9 patients treated with trimethoprim-sulfamethoxazole and rifampin for 8 to 12 weeks plus streptomycin for the first 3 weeks. Longer duration and combination of antibiotic therapy seem warranted to improve outcome and to prevent relapses.