Several studies have suggested that forestry workers are at increased risk for certain types of cancer including soft-tissue sarcoma (STS) and non-Hodgkin's lymphoma (NHL). We now report a series of national case-control studies based on the New Zealand Cancer Registry (NZCR). These involved 19,904 male patients with cancer for the period 1980-1984 who were aged 20 years or more at the time of registration. For each cancer site, the registrations for the remaining sites formed the control group. Current or most recent occupational titles were coded. There was an increased risk for STS (OR = 3.24) in forestry workers which was confined to men under 60 years of age at registration. An elevation in risk for NHL (OR = 1.84) was due to an increase in risk for lymphosarcoma and reticulosarcoma (ICD 200) (OR = 3.18). Acute myeloid leukemia was also associated with forestry work, although the estimate of risk was imprecise (OR = 2.24). Among other cancer sites, an increase in risk of neoplasia of the upper gastro-intestinal tract (ICD 150, 151, 152) was demonstrated. Odds ratios were elevated for cancer of the esophagus (OR = 1.77), stomach (OR = 2.22), small intestine (OR = 5.22), gall-bladder (OR = 4.13) and pancreas (OR = 1.79), as well as for nasopharyngeal cancer (OR = 5.56). These increases in cancer risk were not present in sawmill workers in New Zealand during the same period. The factors responsible for the increased cancer risks in forestry workers remain unclear and require further study.