BACKGROUND: The aim of this study was to quantify the change in the number of conceptions and abortions among women younger than 18 years in England in relation to the government's national teenage pregnancy strategy. METHODS: We undertook geographic analysis of data for 148 top-tier local authority areas. The main outcomes were changes in under-18 conceptions, abortions, and births between the 5-year period before implementation of the strategy (1994-98) and the period immediately after implementation (1999-2003). FINDINGS: The number of teenage conceptions peaked in 1998, then declined after the implementation in 1999 of the teenage pregnancy strategy. Under-18 conception rates fell by an average of 2.0% (95% CI 1.8 to 2.2) per year between 1998 and 2003, below the rate needed to achieve the target of 50% reduction by 2010. The net change between 1994-98 and 1999-2003 was a fall in conceptions of 3.2% (2.6 to 3.9) or 1.4 per 1000 women aged 15-17 years, a rise in abortions of 7.5% (6.5 to 8.6) or 1.4 per 1000, and a fall in births of 10.6% (9.9 to 11.3) or 2.8 per 1000. The change in the number of conceptions was greater in deprived and more rural areas, and in those with lower educational attainment. The change was greater in areas where services and access to them were poorer, but greater where more strategy-related resources had been targeted. INTERPRETATION: The decline in under-18 conception and birth rates since 1998 and evidence that the declines have been greatest in areas receiving higher amounts of strategy-related funding provides limited evidence of the effect of England's national teenage pregnancy strategy. The full effect of local prevention will be clear only with longer observation, and substantial further progress is needed to remedy England's historically poor international position in teenage conceptions.