Occupational and social class differences in cancer mortality among New Zealand males aged 15-64 are examined for the period 1974-78. Age-standardized cancer mortality rates are presented for the Registrar General's social classes as well as for each of six occupational orders and 79 occupational groups. The rates for specific cancer sites are also presented for each social class and for those occupational groups with significantly elevated relative risks. The findings of the social class analyses were generally consistent with those of recent British studies with mortality from cancer of the liver, larynx, lung, buccal cavity and stomach being particularly high in the lower social classes and mortality from multiple myeloma, malignant melanoma and lymphatic leukaemia being particularly high in the upper social classes. The findings of the occupational group analyses were also generally in line with those of recent British studies and those associations which have been found in British studies and were also present in the New Zealand data are discussed. It is concluded that there are a number of associations which warrant further investigation including: large bowel cancer in woodworkers and printers; bladder cancer in hairdressers and beauticians; and malignant lymphoma in farmers.