The aim of this study was to determine how often methicillin-resistant Staphylococcus aureus (MRSA) is found in aerosols while health care workers were undertaking routine care of patients (e.g. taking blood pressures, making beds). Air sampling was conducted using an air sampler and environmental settle samples in single rooms of patients who were either colonised or infected with MRSA, using a Merck MAS -100 air sampler and MRSA chromogenic agar. The air samples and environmental settle samples were collected between the 0700 and 1530 hrs over a ten day period. A totla of 99 air samples and 26 environmental settle samples were collected: 29/99 (29%) of the air samples and 5/26 (19%) of the environmental settle samples were positive for MRSA. Of the ten rooms sampled, eight (80%) had MRSA present in air samples. Concentrations ranged from 1 to 128 colony-forming units per cubic metre. Thus MRSA can frequently be aerosolised. Although the overall contribution of aerosolisation in the transmission of MRSA is unclear, these findings add further evidence to justify the use of gloves and gowns for staff having contact with MRSA-positive patients or going into the rooms, as environmental contamination is likely to be frequent. Masks should be used more often, especially whenever activities likely to generate aerosols occur, such as bed-making, sputum suction or chest physiotherapy.