The association between exposure to ETS and the risk of lung cancer in life-time non-smoking women was investigated by means of a hospital based case-control study in Moscow, Russia. The main importance of our study is that it was conducted on a population with a specific smoking pattern from which no information is available on health effects of ETS. A total of 189 incident cases of histologically confirmed lung cancer were identified in 2 principal cancer treatment hospitals in Moscow. A total of 358 female oncology patients from the same hospitals were selected as controls. The controls matched by the hospitals to the cases were similarly restricted to never-smokers. Women diagnosed with cancer of the upper respiratory organs were ineligible for selection as controls. Personal interviews of cases and controls were conducted in the hospital wards, using a closed-form structured questionnaire. An elevated risk of lung cancer was observed in women whose husbands smoked. The odds ratio (OR) adjusted by age and education for husband's smoking was 1.53 (95% CI, 1.06-2.21). Smoking by other members of the family, by colleague's, or by fathers in the women's childhood do not affect the risk of lung cancer. The risk is higher for women whose husbands smoke ''papirosy'' (OR 2.12; 95% CI, 1.32-3.40), a special Russian type of cigarettes with a long mouthpiece, and usually very high levels of tar (G30 mg/cig) and nicotine (G1.8 mg/cig). Our study suggests that the association between exposure to ETS of the spouse and risk of lung cancer in non-smoking women is somewhat stronger for squamous-cell carcinoma (OR, 1.94; 95% CI, 0.99-3.81) than for adenocarcinoma (OR, 1.52; 95% CI, 0.96-2.39).