The objectives are to describe smoking habits among 11-15-year olds in Denmark in the period 1984-1994 and to describe the association between smoking and social background factors. The article reports data about children at the age of 11, 13 and 15 years from four cross-sectional studies in 1984-1985, 1988, 1991 and 1994 (n = 678, 1667, 1860 and 4046) based on stratified random samples of schools. Data were collected by standardized questionnaires. Median age for first smoking experience changed from approx 12 years in 1984-1985 to approx. 14 years in 1994. The proportion of smokers among 15 year-olds is almost unchanged from 1984 to 1994. In 1994, the proportion of smokers is respectively 2% and 4% among 11 year-old girls and boys, 16% and 11% among 13 year-old girls and boys, and 33% and 25% among 15 year-old girls and boys. The proportion of girls and boys in the three age groups respectively who smoke every day is 0%, 1%, 3%, 4%, 17%, and 11%. In conclusion, smoking habits among children changed considerably from the 1950's to 1980's. The smoking habits have not changed much since the 1980's apart from a slight delay in first smoking-experience.