Serratia marcescens colonises contact lenses during wear, although the frequency of isolation is generally low (0.6% contamination rate). A method for typing the S. marcescens colonising the eye or contact lens was developed, based upon ribotyping, serotyping and biotyping. Twelve different types of S. marcescens were isolated from the eyes, contact lenses, contact lens cases and fingers of contact lens wearers in the Sydney area over a 2-year period. There was no evidence of a specific type being more readily able to colonise the contact lenses than other types. Indeed, eight S. marcescens strains were isolated from the lenses and these belonged to seven types. The diversity of types isolated from the eye indicates that there is probably not a subset of S. marcescens that can colonise the eye, although the results suggest that the types of strains isolated from contact lenses are different from those isolated from nosocomial infections.