Both family structure and processes have been associated with young people's sexual behaviour, but most studies are cross-sectional and focus on only one outcome: age at first intercourse. This paper uses longitudinal data from a survey of Scottish teenagers (N=5041) to show how low parental monitoring predicts early sexual activity for both sexes (with some reverse causation), and for females it also predicts more sexual partners and less condom use. A lot of spending money also predicts early sexual activity and, for males, having more sexual partners. Comfort talking with parents about sex, however, seems to bear little relationship to sexual behaviour.