A total of 842 staphylococci isolated from clinical material over an eight-month period and regarded as probable pathogens were identified according to lyogroup. Almost half the isolates belonged to lyogroups other than lyogroup I (Staphylococcus aureus), suggesting that coagulase-negative staphylococci are increasingly involved in human infections. All isolates were tested for sensitivity to 12 antibiotics. A greater resistance was observed in non-lyogroup I isolates, which again suggests a pathogenic significance of coagulase-negative staphylococci. Only lyogroup I strains, however, were obtained more frequently from clinical isolates than from healthy human skin. The distribution of the isolates in each lyogroup according to their clinical source is reported.