In Denmark the number of births and induced abortions among teenagers has reduced and teenage parenthood is now rare. This paper evaluates the correlation between this observed fertility and reported sexual and contraceptive behaviour. In 1989 a sample of 16–20-year-olds in Denmark was selected at random and personally interviewed about sexual and contraceptive behaviour. Ninety-five per cent of the young women who had experienced sexual intercourse used contraception at the most recent sexual intercourse. In order to support the validity of this finding a model was developed to estimate an expected number of conceptions in the age groups concerned. The model included both the information on coital frequency and use of contraception from the questionnaire and available efficacy rates on contraception. The estimates derived by the model were compared with the registered number of births and induced abortions derived from public registers. The analysis revealed a high accordance between the estimated number of conceptions and the registered number of births and induced abortions for each age group. This underlines the validity of the data on sexual and contraceptive behaviour sampled among teenagers in Denmark. The findings indicate that contraceptive failure is a much greater problem than non-use of contraception for teenagers in Denmark.