Cutaneous and mucosal carriage of Staphylococcus intermedius was investigated in six healthy beagles before and after application of fusidic acid to mucosal surfaces as 1 per cent viscous eye drops twice daily for seven days. Bacterial populations were determined repeatedly over four weeks using quantitative techniques. The overall cutaneous populations of S intermedius reduced significantly (P<0·01) two days after treatment but returned to pretreatment levels after a further week. The mucosal frequency of S intermedius reduced significantly (P<0·001) two days after treatment and remained reduced (P<0·01) at the end of the study. The mucosal populations were also reduced (P<0·01) two days after treatment and remained lower (P<0·05) after a further week. No such changes occurred in the control group of six beagles. The study indicates the importance of mucosae as carriage sites for S intermedius in dogs. This form of therapy may be useful as an additional tool against canine recurrent pyoderma.