Several studies have indicated a high prevalence of hand warts in meat handlers, although the reasons for this are not clear. The high prevalence may be partly due to HPV7, a virus found almost exclusively in meat handlers, but the source of HPV7 is not known. We have carried out a cross-sectional survey of hand warts in male meat workers and controls from other occupational groups, to investigate the reasons for the high prevalence of warts, and particularly of HPV7, in butchers. We studied 240 abattoir workers, 246 retail and wholesale butchers, 308 engineering fitters and 292 office workers. Each subject was interviewed using a standard questionnaire, and his hands were examined by a dermatologist. Scrapings from the warts were tested for HPV1, HPV2 and HPV7 by a polymerase chain reaction method. The prevalence of hand warts was 33.3% in the abattoir workers, 34.1% in the butchers, 19.5% in the engineers and 14.7% in the office workers. Scrapings were taken from 247 of 267 subjects with warts, and HPV DNA was detected in 151 samples. The most common viruses were HPV2 (94 men) and HPV7 (76 men). The excess of warts in meat workers was largely due to HPV7, which was found in only two of the office workers, and was not found in any of the engineers. Logistic regression analysis showed no association between the prevalence of hand warts (or HPV2 and HPV7 specifically) and hand trauma, cold and wet working conditions, smoking, atopy, or handling any particular kind of meat. We suggest that some constituent of animal flesh predisposes to replication of HPV7 in keratinized epithelium.