This report is based on responses to a mailed questionnaire from 927 patients with lung cancer (730 men, 197 women), or their next of kin, and information obtained from the Saskatchewan Cancer Foundation Tumour Registry. Women were diagnosed at an earlier mean age than males (means +/- SE, 63.5 +/- 0.85 years versus 67.6 +/- 0.37 years, P less than 0.001), a finding which was consistent for each major histologic type. Women were more frequently diagnosed before age 60 years (42.0%) than were men (25.6%) (P less than 0.001). Female patients were significantly more likely to be lifetime nonsmokers of cigarettes than male patients (23% versus 3.7%, P less than 0.001). Among current smokers, women started smoking at an older age (19.3 +/- 0.69 versus 16.5 +/- 0.21 years, P less than 0.001), smoked for fewer years (41.0 +/- 1.2 years versus 47.4 +/- 0.57 years, P less than 0.001) and smoked slightly fewer cigarettes per day than male patients (23.6 +/- 1.0 versus 26.7 +/- 0.63, P less than 0.05). Similar results were found for the duration of the smoking habit and number of cigarettes smoked among exsmokers. When current smokers and exsmokers were combined, the distribution of pack years by gender was significantly different. A higher percentage than expected of women as compared to men, are clustered in the lower pack-year categories (P less than 0.0003). No occupational exposure or familial factors which might act in synergism with cigarette smoking were identified. Thus, women developed primary lung cancer at an earlier age while smoking for fewer years than men.