['Surgical site infection (SSI) can be a problematic complication of Mohs micrographic surgery (MMS). Previous reports have cited nasal Staphylococcus aureus (S.\u2009aureus) carriage as a risk factor for SSI, but none thus far in dermatologic surgery.', 'The aim was to determine the difference in infection rates between nasal carriers of S.\u2009aureus and non-carriers, and whether decolonisation with intranasal mupirocin ointment and chlorhexidine wash would reduce the infection rate in nasal carriers.', 'In all, 738 patients presenting for MMS at the Oxford Day Surgery and Dermatology underwent a nasal swab to determine their S.\u2009aureus carriage status. S.\u2009aureus carriers were randomised for decolonisation with intranasal mupirocin ointment and chlorhexidine body wash. Non-carriers were untreated. All patients were followed up for SSI.', 'The rate of SSI was 11 per cent in untreated S.\u2009aureus carriers, 4 per cent in treated carriers, and 3 per cent in non-carriers. The difference in infection rate between carriers and non-carriers was significant (P\u2009<\u20090.001). The difference between treated and untreated carriers was also significant (P\u2009=\u20090.05).'] Is nasal carriage of Staphylococcus aureus in patients undergoing Mohs micrographic surgery an important risk factor for postoperative surgical site infection : a prospective randomised study?