—Cancer incidence of 20 529 hypertensive patients included in the community-based hypertension register of the North Karelia Project was determined. A total of 2511 incident cancer cases were obtained among the patients in record linkage with the nationwide Finnish Cancer Registry during the mean follow-up time of 16 years. The age-adjusted incidence rates per 100 000 person-years were 248.4 for men and 171.7 for women, which correspond to that of the general population in the area. The Cox regression model was used to analyze the effect of hypertension-related variables on cancer incidence. In men, the diastolic blood pressure was associated with an increased cancer risk but only in those who smoked >10 cigarettes per day. The functional diagnosis of hypertension (stage I, hypertension with no end-organ damage; stage II, hypertension with left cardiac hypertrophy; and stage III, hypertension with extracardiac organ damage) was associated with the increased risk significantly in men who used antihypertensive drugs at baseline. In women, the diastolic blood pressure was associated with an increased cancer risk in those who did not use antihypertensive drugs at baseline. The functional diagnosis of hypertension was associated with an increased risk only in those who smoked >10 cigarettes per day, but the number of women and cancer cases in this group was small. These results indicate a complex pattern of diastolic blood pressure, functional diagnosis, use of antihypertensive drugs, smoking, and gender in the cancer risk of hypertensive patients.