During the year 1987, 106 cases of human brucellosis were studied prospectively at the Jordan University Hospital. The disease was more often diagnosed among adults (73.6%) than children (26.4%). Serious clinical complications were observed in 5.7% patients. An initial Brucella antibody titre greater than or equal to 160 proved to be reliable in confirming suspected cases of acute and subacute brucellosis. Culture of blood was found to be more sensitive (44.4%) and significant (P less than 0.02) than bone marrow culture (27.7%) for detecting Brucella melitensis. All patients treated with rifampicin plus tetracycline or co-trimoxazole were considered to be clinically cured by disappearance of all major clinical features of brucellosis. By contrast, 2/10 patients treated with rifampicin alone, as well as 1/56 patients treated with tetracycline and streptomycin, clinically relapsed. It is evident from this study that the treatment with rifampicin alone is not as effective in brucellosis as it is when given with another appropriate drug.