Rational choice models of teenage sexual behaviour lead to radically different predictions than do models that assume such behaviour is random. Existing empirical evidence has not been able to distinguish conclusively between these competing models. I use regional data from England between 1998 and 2001 to examine the impact of recent increases in access to family planning on teenage pregnancy and sexually transmitted infection diagnosis rates. I find consistent evidence that access to family planning services is not associated with reductions in teenage pregnancy rates. I also find consistent evidence that increased promotion of emergency birth control in youth family planning clinics has not affected the relationship between clinic services and teenage pregnancy rates, but has significantly worsened the relationship between clinic services and teenage sexually transmitted infection diagnosis rates. Most of the observed relationships are inconsistent, with teenage sexual behaviour being the result of a random decision-making process. (Contains 5 tables and 10 notes.)