Cancers of the skin are not properly registered and our lack of precise knowledge of the influence of environmental factors is due both to a failure to report and a failure to attribute because many tumours are not recognised as due to environmental factors and escape notification due to lack of knowledge and teaching. The long latent period also interferes. The commonest cancer is squamous cell carcinoma followed by basal cell carcinoma. Melanoma is exceedingly rarely environmental. The main causative agents are: Polycyclic aromatic hydrocarbons (PAH), inorganic arsenic and ionising radiation. PAH induce 4 times more cancer of the scrotum in workers using cutting oils or pitch than expected. These subjects have also increased incidence of second primaries of both the skin and internal organs. The latent period varies from 20 years (exposure to coal tar) to 50 years or more (exposure to mineral oils). Exposure to pitch may result in 11 fold increase incidence of squamous cell carcinoma. Skin cancer due to arsenic is rare. It has been seen in sheep dip workers, in patients treated with Fowler's solution and in vineyard workers using arsenical pesticides and drinking contaminated wine. The latent period may go up to 60 years. Ionising radiation over 1,000 rems may cause basal and squamous cell carcinoma. The latent period varies from 7 weeks to 56 years (average 25--30 yrs).