Methicillin-resistant Staphylococcus aureus (MRSA) infection in a cystic fibrosis (CF) unit was investigated. Two typing methods, phage-typing and restriction fragment length polymorphism (RFLP) by pulsed-field gel electrophoresis (PFGE) and phylogenetic analysis, showed that nonsocomial transmission of MRSA from the general hospital population had occurred. One instance of possible transmission between two patients was identified. However, transmission between two family members did not occur indicating a minimal risk of MRSA acquisition from social contact compared with hospital admission. This study supports policies for limiting CF-patient admission to hospital but transmission of MRSA does not appear to be a reason for limiting social contact with other CF patients.