General practice characteristics are important for healthcare providers to maximise outcomes. Although different aspects of general practice characteristics have been studied previously, the impact of practice size on the delivery of care has been sparsely studied, particularly in relation to diabetes care. This brief report presents a longitudinal study in Shropshire (66 practices, 16,858 patients with diabetes) to assess the impact of practice size on diabetes care before and after implementation of the Quality and Outcomes Framework (QOF). Achievement of glycaemic control targets was better before the QOF for larger as compared to smaller practices (P=0.02 and P=0.003 for haemoglobin A1c [HbA1c]<or=7.4% and 10% respectively). This difference disappeared following QOF implementation. Repeated measures analysis showed significant improvement in achieving glycaemic control targets following QOF implementation in both large and small practices (P<0.001 for HbA1c<or=7.4% and 10%). The study failed to reveal an impact of practice size on achieving the HbA1c target<or=7.4% (P=0.1) by this analysis. However, it did show an impact on reaching the target of HbA1c<10% (P=0.04) in favour of smaller practices. There was a significant difference in favour of smaller practices for achievement of prescription of angiotensin-converting enzyme inhibitors (P=0.001).