Twenty-one patients were included in an open randomized study comparing vancomycin 1 g bd with teicoplanin 400 mg daily in severe methicillin-resistant Staphylococcus aureus infections. The median duration of therapy was 15 days for vancomycin and 21 days for teicoplanin. Most patients presented with severe underlying conditions, such as major surgery (8), solid tumours (5), multiple trauma (3). The infections treated, included septicaemia, osteomyelitis, bronchopneumonia, cellulitis and acute pyelonephritis. Mean MICs of the strains were 0.39 mg/l for vancomycin and 0.195 mg/l for teicoplanin. Mean trough and peak serum concentrations of vancomycin were 14.3 +/- 5 mg/l and 34.3 +/- 13 mg/l, while the teicoplanin values were 7.5 +/- 4 mg/l and 17 +/- 7 mg/l. The cure rate was seven of 12 in the teicoplanin group and six of nine in the vancomycin group, with four and three cases, respectively, of improvement and one failure in the teicoplanin group. Transient renal impairment occurred in two cases with both regimens; superinfection and colonization in three patients and one patient, respectively, with both regimens.