Smoking is a risk factor associated with high and preventable mortality and morbidity. An understanding of smoking consolidation and the desire to quit in specific subgroups of the general population will facilitate appropriate planning of health care resource utilization. We performed a multistage, random, stratified cross-sectional study in the general population of Valladolid (Spain) during 1998 and 1999 as part of a cardiovascular disease risk survey. Data collected by questionnaire and interview included number of cigarettes smoked per day, nicotine dependence and stage in the process of smoking cessation. Venous carboxyhemoglobin was also measured. The percentage of reported smokers in the general population was 29.3% (95% CI: 25.7-32.9%). Prevalence was 41.8% (95% CI: 39.2-44.5%) in the 26-to-45-year-old age group and fell to 6% (95% CI: 5.6-6.5%) among subjects over 66 years of age. Analysis by sex, 31.2% (95% CI: 26.1-36.4%) of men and 27.4% (95% CI: 24.1-30.7%) of women were smokers. In rural areas the percentage of smokers was 26.9% (95% CI: 20.2-33.5%) whereas the percentage in urban areas was 31.2% (95% CI: 26.1-36.4%). The number of cigarettes/day, venous carboxyhemoglobin and nicotine dependence differed by age range, sex and place of residence and helped to describe the degree of consolidation of smoking by strata. Phases of cessation were distributed similarly by age range but not by sex. The prevalence of smoking is still high, particularly among young people and women, although it is tending to decrease. Smoking is better established in the 26-45 year-old age range, among men, among those living in rural areas and among older smokers who, probably, can not quit smoking alone.