The trends of age-gender specific prevalence of self-reported smoking habits are presented, observed in two population surveys, performed in 1986-87 and 1989-90 in Area Biranza, a northern Italian industrialized district where a WHO MONICA Centre is located. Methods were internationally standardized to obtain comparable data on two independent random samples, each composed of 1,600 subjects, age-sex stratified and extracted from the 25-64 year old residents. A closed question interview was administered to identify smoking condition (smoker, past-smoker, occasional smoker, never smoker), number of cigarettes consumed per day and attained educational level, categorized in compulsory school and post-compulsory school. Serum thiocyanate was measured as a validation index, using a cutpoint of > 100 mumol l-1 to detect false negatives. Trends in smoking prevalence are analyzed taking into account influences of education in the presence of an anti-smoking policy that was started in Italy toward the end of the eighties. Self-reported data, confirmed by serum thiocyanate, show a consistent decline of smokers among males (from 48 to 41%), more evident in younger age groups. In females, smoking prevalence is stable (23-24%), although thiocyanate levels in the whole samples indicate a slight but significant tendency to decrease. Education demonstrates positive influences against smoking, particularly in younger male classes. In females a crossover effect is observable: in the second survey youngest group, education results protective against smoking; the contrary is true in the older groups. Our data, detailing what was initially recognized in previous Italian surveys, may be useful to specify the directions of future preventive actions.