To evaluate the effect of cigarette smoking on lung cancer by tumor location and histological type, we compared the smoking history obtained from medical records of 605 patients with squamous cell carcinoma (194 males and 10 females) or adenocarcinoma (219 males and 182 females) of the lung and 183 patients with metastatic lung cancer (82 males and 101 females) who had been aged 40 years or over at the time of surgical resection at the Cancer Institute in Tokyo from 1973-1991. The tumors which developed in a main or segmental bronchus were classified as central type, and those in a subsegmental or more distal bronchi were categorized as peripheral type. Cases with adenocarcinoma were classified by a pathologist into two histological subtypes, papillary and tubular types, according to the WHO lung carcinoma classification. Risk of squamous cell carcinoma was strongly associated with cigarette smoking for both central (OR (odds ratio) = 10.3 in males and 4.4 in females) and peripheral sites (OR = 10.7 in males and 6.5 in females). There was no significant association between cigarette smoking and adenocarcinoma for any tumor site or histological subtype in both sexes.