Cutaneous malignant melanoma (CMM) rates have been increasing in the United States at an average rate of about 4% per year. In 1987, it was estimated that there would be 25,800 cases and 5,800 deaths from CMM in the United States. The exact cause of the increase in unknown, but there is evidence to suggest that increasing exposure to the ultraviolet B (UVB) radiation present in sunlight may be partly responsible. The evidence includes: 1. the fact that higher CMM incidence rates are observed in people with lesser amounts of skin pigment (which blocks penetration of UV); 2. a correlation of higher CMM rates with decreasing latitude and increasing UVB levels; 3. the observation that freckles and nevi (precursors to CMM) are induced by solar exposure; 4. differences in CMM rates between natives and immigrants to sunny climates; 5. high rates of CMM in patients who cannot repair UVB-induced DNA damage; and 6. the indication that sun exposure at early ages and of an intermittent nature results in higher CMM risks. With the concern that depletion of stratospheric ozone could result in increasing levels of UVB, it has become important to understand the relationship between UVB and CMM in order to estimate the increases in CMM that would be expected with ozone depletion. When empirical relationships between UVB and CMM incidence and mortality rates were derived and used to estimate the impact of stratospheric ozone depletion, a 1% depletion of ozone was predicted to result in increases of 1%-2% in CMM incidence and 0.8%-1.5% in CMM mortality.