Aim of the investigation was to study the frequency and prognosis of patellar chondropathy in general practice. As far as the frequency was concerned a secondary analysis was done of data from the Nijmegen Continuous Morbidity Registration (4 general practices, 12,000 patients). The prognosis was studied in patients in these practices with at least one episode of patellar chondropathy in the years 1985-1988. The GPs were asked about the diagnostic criteria they used. The registration showed an average of 6 new cases of patellar chondropathy per 1000 patient-years; in 7% of the cases the GPs referred a patient for specialist care. To study the prognosis patients were asked to fill in a questionnaire. Response was 84%, 178 questionnaires were analysed. The female-male ratio of the respondents was 2, 60% were younger than 60 years. In 44% of the cases the complaints subsided within 6 months. Interventions such as X-ray and physiotherapy depended on severity, duration and frequency of the knee complaints.