A cross-sectional study of 178 asymptomatic contact lens wearers attending 10 contact lens practices in the west of Scotland was conducted over a 4 month period. The aims of the study were to identify specific microbial contaminants in lens cases, to determine the rate of contamination of such containers and to assess the value of the steps involved in different lens care regimens in the prevention of case contamination. Microbial contamination affected 53% of lens cases. Cases used with conventional wear and disposable systems were contaminated at similar rates and, therefore, the advantage of regular lens replacement may have been lost if these lenses were stored in contaminated cases. Four percent of lens cases were contaminated with amoebal species and all of these showed concomitant bacterial colonisation. These findings imply that case hygiene is probably as important as lens hygiene if new or disinfected lenses are not to be immediately re-contaminated by storage in dirty cases. Unfortunately simple and effective methods of lens and case disinfection, which would be suitable for use in the average home environment, are not yet available. It follows that frequent and regular disposal of lens cases may prove to be a necessary measure to prevent the build-up of microbial colonisation in such containers.