OBJECTIVE: To evaluate the prevalence of, attitudes towards, and knowledge about cigarette smoking in Ecuador in 1991. DESIGN: Survey using in-person interviews; stratified and multiple regression analyses. SUBJECTS AND SETTING: Eight hundred people (> or = 18 years old) representative of the adult populations in the cities of Quito and Guayaquil, Ecuador. MAIN OUTCOME MEASURES: Smoking prevalence, daily cigarette consumption, reasons for smoking, desire to quit smoking, knowledge about the health effects of smoking. RESULTS: About a third of the population in the two major cities of Ecuador are cigarette smokers. Men are not only more likely to be smokers than women (45% vs 17%, respectively), but when they do smoke, they also smoke significantly more cigarettes per day (60% more) than women. Cigarette smoking appears to be more common among younger populations, and among more educated people. Housekeepers are significantly less likely to be smokers compared with people in other occupations. About 80% of smokers consume fewer than 10 cigarettes per day. In Quito, a 40% increase in the number of cigarettes smoked per day on weekdays compared with weekends suggests an effect of the environment on smoking patterns. About 60% of smokers stated their desire to quit smoking, and there was almost universal knowledge about the harmful effects of cigarette smoking on the health of active and passive smokers. CONCLUSIONS: About a third of the population in the two major cities of Ecuador reported smoking cigarettes. Smoking is more common among men, those of younger age, and the more educated. The findings in this study should help the development of antismoking policies in Ecuador and other countries in the region.