Exposure to a variety of environmental factors associated with cancer occurrence varies by social class. These factors include air pollutants (SO2, NO2, total suspended particulates, etc.), toxic waste hazards, and ionizing and other radiation. Heavy environmental pollution has been associated with an increased risk of some cancers and in particular lung cancer. There is limited evidence suggesting that individuals from lower social classes are exposed to higher levels of environmental pollutants than are individuals from higher social classes. This may be due to the placement of new sources of pollution or of toxic processes in disadvantaged areas, or to the selective migration of the poorer sectors of society to these areas. The available data do not allow any conclusion on the possible contribution of exposure to environmental pollution to social class differences in cancer occurrence. Exposure to ultraviolet (UV) radiation, principally from sunlight, is modified strongly by personal behaviours such as choice of recreation and use of protective clothing. Those in outdoor occupations are likely to receive the highest cumulative exposure to UV radiation. There is no clear evidence from recent survey research in Australia and North America that socioeconomic factors are strongly related to non-occupational exposure to UV radiation. Information is lacking on the influence of socioeconomic status on sun exposure in other parts of the world. There is little information on the social distribution of exposure to ionizing radiation.