The findings are reported from a New Zealand Cancer Registry-based case-control study involving 427 male patients with testicular cancer registered during the period 1979-1983 and aged 20 years or more at time of registration. Controls were also males chosen from the Cancer Registry with two controls per case, matched on age and year of registration. It was found that, as in other countries, persons in the upper social class groupings were at increased risk of testicular cancer. Persons in professional occupations were also at increased risk, but the odds ratio of 1.09 was much smaller than found in other studies. The previously reported excess risks for farmers, food and beverage workers, forestry workers, and pulp and paper workers were not supported by the New Zealand data. On the other hand, the previously reported excess risk for sales and service workers including members of the armed forces was supported, to some extent, by the New Zealand data with odds ratios of 1.38 (95% confidence limits 0.98-1.93) and 2.15 (95% confidence limits 0.80-5.79), respectively. Other groups with elevated risk include: physicians (odds ratio = 6.50, 95% confidence limits 1.29-32.6); production supervisors (odds ratio = 2.85,95% confidence limits 1.00-8.13); and motor vehicle mechanics (odds ratio = 2.02, 95% confidence limits 0.93-4.42). However, the New Zealand data generally does not suggest that occupational factors (or lifestyle factors associated with occupation) are of major direct importance in the etiology of testicular cancer. The incidence of testicular cancer has a bimodal age distribution in New Zealand and has risen markedly during the period 1948-1979. The New Zealand data differed from patterns observed in other countries in that the relative increase was approximately uniform across age groups rather than being stronger in the younger age groups.