Health care workers are exposed to various occupational hazards. In a register linkage study we investigated cancer incidence in health care personnel in Denmark. The overall cancer incidence was elevated in female general and dental practitioners. Male doctors had a risk of brain cancer twice as high as expected. Male dental practitioners, female hospital doctors and nurses had significantly high risks of melanomas of the skin. The breast cancer risk was elevated among female salaried dentists, hospital doctors, and nurses. Female cleaners had a significantly elevated risk of leukemia (31 cases, SIR 1.54). The lung cancer risk was low in several occupational groups. This indicates a change in risk behavior related to tobacco smoking. A high risk of skin melanomas may indicate that behaviour related to sunlight exposure has not changed.