A computer omnibus survey to determine the prevalence of onychomycosis in the United Kingdom was carried out in the early part of 1990. A total population of 9322 adults, aged 16 years and over, was interviewed face-to-face, and a questionnaire completed, which consisted of questions and photographs of various nail dystrophies, including onychomycosis. The results in the population surveyed revealed a prevalence of dermatophyte nail infection of 2.8% in men and 2.6% in women. In the group aged 16–34 years, the prevalence rate was 1.3%; this increased to 2.4% in the group aged 35–50 years, and to 4.7% in those aged 55 years or over. Of those found to have onychomycosis, 27% had sought advice from a chiropodist and less than 12% had consulted a specialist. These results suggest that nearly 1.2 million people in the UK have a fungal nail infection and the majority had not sought medical advice, although over 80% stated that they would do so if they were aware that their nail disorder was of fungal origin. A similar proportion would wish to be treated if an effective treatment was available.