Between 1979 and 1990, the incidence rate (World Standard) for cancer of the prostate in the region of Isère (France) increased from 22.1 to 45.0 cases per 100,000 men, although there was no concurrent increase in mortality (16.0 to 17.6 cases per 100,000 men). This represents a mean increase per year of 6.3% for incidence, compared with 1.3% (NS) for mortality. Incidence of cases with metastases at diagnosis also remained stable with time. In this area, Prostatic Specific Antigen assays began in 1987, and rectal ultrasonography was implemented in 1984, but activity peaked only in 1988. Thus, during 1986-1988, there was both an implementation of new diagnostic procedures and an increase in the incidence of prostatic carcinoma, which suggests that the latter was the result of increased detection of small latent carcinomas. This has implications for public health since apart from increasing costs, it might unduly disturb the life of otherwise healthy people.