This paper examines whether improved access to family planning services for under 16 is likely to help in achieving the aim of reducing underage conceptions. A simple model of rational choice is introduced which suggests that family planning increases rates of underage sexual activity and has an ambiguous impact on underage conception and abortion rates. The model is tested on panel data on regions within the UK using two approaches. The first test is whether the 1984 Gillick ruling had a differential impact on two groups: under 16 for whom access to family planning was restricted by the ruling and older teenagers who were not affected. Secondly, attendance by under sixteens at family planning clinics, suitably instrumented, is used as a proxy for access to family planning. With both approaches, no evidence is found that the provision of family planning reduces either underage conception or abortion rates. Socio-economic variables such as children in care rates and participation rates in post-compulsory education are found to be significant predictors of underage pregnancies.