OBJECTIVE: To investigate whether the incentive scheme for UK general practitioners led them to neglect activities not included in the scheme. DESIGN: Longitudinal analysis of achievement rates for 42 activities (23 included in incentive scheme, 19 not included) selected from 428 identified indicators of quality of care. SETTING: 148 general practices in England (653 500 patients). MAIN OUTCOME MEASURES: Achievement rates projected from trends in the pre-incentive period (2000-1 to 2002-3) and actual rates in the first three years of the scheme (2004-5 to 2006-7). RESULTS: Achievement rates improved for most indicators in the pre-incentive period. There were significant increases in the rate of improvement in the first year of the incentive scheme (2004-5) for 22 of the 23 incentivised indicators. Achievement for these indicators reached a plateau after 2004-5, but quality of care in 2006-7 remained higher than that predicted by pre-incentive trends for 14 incentivised indicators. There was no overall effect on the rate of improvement for non-incentivised indicators in the first year of the scheme, but by 2006-7 achievement rates were significantly below those predicted by pre-incentive trends. CONCLUSIONS: There were substantial improvements in quality for all indicators between 2001 and 2007. Improvements associated with financial incentives seem to have been achieved at the expense of small detrimental effects on aspects of care that were not incentivised.