The prevalence of smoking in pregnancy has been analyzed in a surveillance of women delivering between February and March 1989 in a large maternity clinic in Milan, Northern Italy. Out of the 411 interviewed women, 133 (32%) were current smokers before and 71 quit smoking during pregnancy. The probability to quit smoking decreased with increasing age and was lower in less educated women; these findings were however not statistically significant. Considering persistent smokers only, the mean number of cigarettes per day decreased from 13 before pregnancy to 8 during gestation; this finding was generally consistent in various subgroups of age and education. These reduction, however, are probably overestimated, since they are based on women's report only. Thus, these findings indicate that there is still ample scope for intervention on smoking in pregnancy, particularly in older and less educated women.