BACKGROUND: The feasibility, cost-effectiveness and best means to implement population screening for type 2 diabetes remain to be established. OBJECTIVE: To learn from the experiences of practice staff undertaking a diabetes screening programme in order to inform future screening initiatives. METHODS: Qualitative analysis of interviews with staff in six general practices in the 'ADDITION-Cambridge' trial; three randomly allocated to intensively manage screen-detected patients and three providing usual care. We conducted semi-structured interviews with seven nurses, four doctors, three health care assistants and four managers. Four researchers analysed the transcripts practice by practice, preparing vignettes and comparing interpretations. Participants commented on a summary report. RESULTS: Each practice team implemented the screening and intervention programme differently, depending on numbers at risk and decisions about staff contributions. Several emphasized the importance of administrative support. As they screened, they extended the reach of the programme, testing patients outside the target group if requested, checking other risk factors, providing health information and following up people with impaired glucose tolerance. Staff felt that patients accepted the screening and subsequent management as any other clinical activity. CONCLUSIONS: Although those developing screening programmes attempt to standardize them, primary care teams need to adapt the work to fit local circumstances. Staff need a sense of ownership, training, well-designed information technology systems and protected time. Furthermore, screening is more than measurement; at the individual level, it is a complete health care interaction, requiring individual explanations, advice on health-related behaviour and appropriate follow-up. The UK 'NHS Health Checks' programme should embrace these findings.