OBJECTIVES: The incidence of prostate cancer has increased during the last two decades. Part of this increase has been attributed to prostate specific antigen (PSA) testing. As a consequence of testing many patients enter treatment at an early stage of the disease. This might be reflected in their health-related quality of life. METHODS: An ongoing observational follow-up study using the 15D generic health-related quality of life (HRQoL) instrument. Patients are asked to fill in the HRQoL questionnaire at baseline and 3, 6 and 12 months after entering treatment, and results are compared with those of an age-standardized general population sample. RESULTS: So far, 587 patients (mean age 66 years) have been assessed at baseline and 336 have completed the one-year follow-up. The mean HRQoL score (on a 0-1 scale) of the patients at baseline was statistically significantly better than that of the general population (0.904 vs. 0.874, p <0.001). Furthermore, the patients were statistically significantly better off than the population on 9 of the 15 dimensions of the HRQoL instrument. Only the dimensions of elimination (i.e. urinating)(p <0.001)  and sexual function (p <0.05) showed statistically significantly worse levels in the patients than in the general population. In patients having completed the one-year follow-up, the total HRQoL score fell from 0.913 to 0.886 (p <0.001). The greatest deterioration was seen in sexual activity (p <0.001). By contrast, elimination did not change in a statistically significant manner during follow-up. CONCLUSIONS: The HRQoL of patients entering treatment is surprisingly good. Although HRQoL of the patients showed slight deterioration during follow-up, patients were on many of the dimensions of the 15D instrument one year after diagnosis still better off than the general population. The only clear exception was sexual activity which showed marked deterioration in the patients during follow-up.