A total of 413 eligible patients took part in an observer-blind randomised multicentre clinical trial in order to compare the clinical and bacteriological efficacy of mupirocin (Bactroban) ointment with sodium fusidate (Fucidin) ointment for treating superficial skin infections seen in general practice. Mupirocin was applied twice daily and sodium fusidate thrice daily for a period of 7 days. Both treatments were similarly effective with 97% patients treated with mupirocin and 93% patients treated with sodium fusidate responding. Mupirocin was significantly more effective in the treatment of acute primary skin infections and in the treatment of a subgroup of patients with impetigo (P less than 0.01). Of the organisms detected before treatment began, 93% were not found after treatment with mupirocin compared with 89% after treatment with sodium fusidate. Staphylococcus aureus and/or beta-haemolytic streptococci appeared to be eliminated in significantly more patients treated with mupirocin (96%) compared with those treated with sodium fusidate (88%), (P = 0.03). Both treatments were well tolerated.