The prevalence of teenage smoking in a cohort of 12,058 subjects born in northern Finland in 1966 is discussed in terms of its social and family determinants, especially in "non-standard" families (with one or more of the parents absent for at least part of the child's upbringing). The prevalence of experimental or daily smoking was 67.4%, the rate being 65.5% in the standard, two-parent families and 75.5% in the non-standard families, the difference being statistically significant (p less than 0.001). The corresponding prevalence of daily smoking was 6.4%, but the rate was 5.1% in standard families and 12.1% in non-standard families (p less than 0.001). An elevated risk of smoking existed among adolescents who had experienced death of their father or divorce of their parents and among girls who had experienced death of their mother. Maternal smoking during pregnancy and maternal age under 20 years at the time of delivery increased the risk, while being the first-born child reduced it. Among family factors existing in 1980, paternal smoking increased the risk for both sexes, while more than three siblings, mother's unemployment or gainful employment (i.e. not a housewife) were associated with smoking by the boys as was urban living, and for the girls migration by the family to a town. The results suggest that juvenile smoking may be a kind of indicator of possible problems experienced by the parents and/or the adolescents themselves with respect to parenthood and family development.