Lifetime job histories from a population-based case-control study of squamous cell carcinomas of the oro- and hypopharynx (OHPC), nasopharynx (NPC), and sinonasal cavity (SNC) were systematically examined to generate new hypotheses as well as to test previously noted associations between occupation and the cancers under study. The effects of both duration of employment in a particular job and the timing of the employment in relation to cancer diagnosis were investigated in a stratified analysis that controlled for cigarette smoking, alcohol intake, and other major risk factors. Overall, data on 231 cases and 552 controls were analyzed. Occupations at increased risk of OHPC included "food service" workers in the "retail trade" industry (odds ratio = 1.9; 95% confidence interval = 1.0-3.6), "vehicle mechanics" in the "repair services" industry (OR = 2.5; CI = 0.8-8.3), "industrial mechanics" (OR = 31.0; CI = 3.0-315.1), and "carpenters" in the "construction" industry (OR = 1.5; CI = 0.7-3.4). For NPC, similar patterns of increased risk were found for "food service" workers and "vehicle mechanics." For "carpenters" in the "construction" industry, the relative risk estimate was almost five (OR = 4.8; CI = 1.2-19.4). Increases in SNC risk were noted for "food service" workers, as well as a number of occupations in the "lumber and wood product manufacturing" industry, including "forestry and logging" (OR = 2.0; CI = 0.5-8.2), and "wood working machine operators" (OR = 7.9; CI = 1.6-39.2). In each of these instances, the relative risk estimates increased with increasing duration in the job and when a 15-year induction/latency period was taken into account.