The nasal carriage rate of Staphylococcus aureus was significantly higher in hospitalized persons (children, adult females and staff) - 53.8%, - than in similar persons at a local clinic - 29.8% (P less than 0.001) - in Ile-Ife, Nigeria. However, unlike studies carried out elsewhere, a higher proportion of S. aureus strains obtained from persons at the clinic were resistant to commonly used antimicrobial agents than were strains isolated in the hospital. This has been attributed to the ease at which these drugs can be obtained by the general population and used unsupervised and indiscriminately. Methicillin was the most effective antimicrobial agent against pathologic staphylococci (2.2% resistance), followed by erythromycin (16.5% resistance), co-trimaxozole (28.0% resistance), chloramphenicol (76.9% resistance), tetracycline (78.6% resistance) and penicillin and ampicillin (97.8% resistance). The widespread resistance of S. aureus to penicillin and ampicillin (and other antimicrobial agents) is of clinical significance in the treatment of post-operative infections, since carriers are reportedly more prone to such infections than are non-carriers.