This study found significant results for cancer types for which no association with ionizing radiation was reported in previous occupational studies. The standardized incidence ratio for melanoma was significantly elevated in males. The excess relative risk was positive, but this result was not statistically significant; in fact, the only occupational category with significant standardized incidence ratios is the dental category, which has the lowest doses. There is little evidence from previous studies that links melanoma even to high doses; for instance, the 1994 report from the United Nations' Scientific Committee on the Effects of Atomic Radiation (1) makes no mention of it. The interpretation of our results for melanoma is therefore unclear. The result could be attributed to chance, in view of the many types of cancer considered in the analysis. It could also be related to lifestyle through exposure to ultraviolet radiation, but there are insufficient data to come to a conclusion in this matter. The excess relative risk for colon cancer is positive in males, but only marginally significant, and the standardized incidence ratio is less than unity. The excess relative risk for colon cancer is positive but not significant in both sexes combined; this is a consequence of the low doses for the females. In view of the absence of previously reported positive findings, it seems reasonable to attribute this result to chance. The excess relative risk for cancer of the testis is significant and very large, but the confidence intervals are wide. The standardized incidence ratio, although not significant, is slightly above 1. This evidence suggests that this type of cancer merits attention in future studies, but the result needs to be interpreted with caution