This article reports an evaluation of the implementation of clinical supervision for nurses in seven pilot sites within a National Health Service Trust in the United Kingdom. Focus groups and documentary analysis informed the development of a set of questionnaires that were used to collect qualitative and quantitative data from all participants within the pilot scheme. The questionnaires were administered twice at 12-monthly intervals during the 2-year study. Overall, the findings demonstrated a favourable response to clinical supervision, with practitioners identifying that it had been most useful for them in reducing professional isolation. However, detailed analysis of the development of clinical supervision within each pilot site revealed that some groups had been more successful than others in achieving a format that was effective and acceptable to all participants. This enabled factors to be identified which contribute to effective clinical support and factors which reduce its effectiveness. A comparison of these findings with those from an earlier study into teacher support teams – a school-based system of peer support for teachers – suggest that both teaching and nursing professionals experience professional isolation. Involvement in peer support, in the form of clinical supervision or teacher support teams, could be effective at reducing this isolation and can thus enable practitioners to meet the requirements of clinical governance or performance management. However, effective peer support in the form of teacher support teams or clinical supervision does not occur spontaneously. A similar set of factors that contribute to the development of effective peer support was evident in both studies. These include formal training in the skills of supervision/support, the successful development of a sense of ownership among practitioners of the model of supervision/support, and ongoing support and facilitation from management and employers.