BACKGROUND Encouraged by the increased purchasing power of general practitioners (GPs), specialist-run clinics in general practice and community health care settings (known as specialist outreach clinics) have increased rapidly across England. The activities of local commissioning schemes within primary care groups are likely to accelerate this trend. AIM To evaluate the costs, processes, and benefits of specialists' outreach clinics held in GPs' surgeries, compared with hospital outpatient clinics. DESIGN OF STUDY A case-referent (comparative) study comparing the characteristics of outreach clinics (cases) with matched outpatient control clinics. SETTING Thirty-eight outreach clinics, compared with 38 matched outpatient clinics as controls, covering 14 hospital trust areas across England. METHOD Self-administered questionnaires were given to patients in both clinic settings. These covered processes, satisfaction, personal costs, and health status, with postal follow-up at six months to assess health outcomes. Self-administered questionnaires were also given to the specialists and GPs whose clinics were included in the study (individual patient clinical sheet and an attitude questionnaire), practice managers, and trust accountants (process and costs questionnaire). Evaluation of the costs, processes, and benefits of specialist outreach clinics versus hospital outpatient clinics was carried out by comparing questionnaire responses. RESULTS In comparison with outpatients, outreach clinic patients spent less time on the waiting lists for appointments to see the specialist, they had shorter waiting times in clinics, fewer follow-up appointments, and were more likely to be completely discharged after the sampled attendance. Outreach patients were more satisfied than outpatients with the range of clinic process items asked about. Most doctors felt that the outreach clinic was 'worthwhile'. While patients' personal costs were lower in outreach than in outpatients clinics, NHS costs were more expensive per patient in outreach. The benefits of outreach clinics on patients' health status at six months' follow-up were relatively small. CONCLUSIONS Outreach clinics are a means of improving access to specialist services for patients, in addition to improving the efficiency and quality of health care. Most results were similar across specialties and areas. The benefits of the outreach service need to be weighed against their substantially higher NHS costs, in comparison with outpatients clinics. Outreach clinics are unlikely to be financially justifiable for NHS funding given that the impact on patients' health status was small.