To provide incidence and prevalence data on breast and colorectal cancer in the Picardie area of France.,An age-period-cohort method was used to estimate regional incidence and prevalence of cancer from regional cancer mortality data and patient survival data recorded in the Somme Cancer Registry.,European standardized breast incidence for 1998 was 110 per 100000 inhabitants. The incidence for colorectal cancer was 67 per 100000 for men and 47 per 100000 for women. Prevalence was 9656 for breast cancer and 6283 (2941 for men and 3342 for women) for colorectal cancer. Incidence of breast cancer increased considerably (80.9%) between 1979 and 1998.,These results provide data on breast cancer and colorectal cancer which are useful for planning demand for healthcare or medical surveillance in the Picardie area.