Breathing other people''s smoke is called passive, involuntary or second-hand smoking. It has two types: 1. Side stream smoking: from burning up of the cigarette. 2. Mainstream smoking: inhaled and exhaled by smoker. Environmental Tobacco Smoke (ETS) is a major source of indoor air pollution.Tobacco smoke contains over 4000 chemicals in the form of particles and gases. Multan (Pakistan) has one of the highest prevalence of passive smoking among women of the East. The objectives are to assess the trend of passive smoking during pregnancy in a five-year period and the determinants of passive smoking cessation during pregnancy in Multan. A 1/6 random sample of all women delivering at the reference hospital of the region for the period 1998-2002 was drawn, 1559 women. Information was obtained from personal interview, clinical chart, and prenatal care records. In the analysis relative risks and 95% confidence intervals were estimated. Multivariate analysis was carried out using stepwise logistic regression.