The prevalence of virus warts of the hands among butchers has been determined in three industrial butcheries by examining 536 meat-workers at their places of work. A prevalance of 23-8% has been found, which is significantly higher than the 8-5% prevalance found in 965 control adult subjects examined in different firms where manipulation of food does not occur. Further, the prevalence of virus warts of the hands has been found significantly higher in the 199 workers of one butchery (32-1%) than in 199 control subjects (10-1%) strictly matched for age and sex, and belonging to the same industrial area. In butchers, warts of the dorsal aspects of the hands are statistically less frequent than in control subjects when three localizations are considered (dorsal, palmar, dorsal plus palmar). No significant difference is observed when single localizations (dorsal or palmar) are considered. A definite explanation of the high prevalence of virus warts of the hands among butchers has not been found so far; some hypotheses are discussed in the light of the presnt study.