CANCER AND CANCER RISK FACTORS AMONG NORTHERN PLAINS INDIANS A pragmatic definition for epidemiology is the study of diseases and health problems as they affect groups of people. Why do we need epidemiologists in Indian Health Service? The main reason is to provide information for action to media, tribal communities, health professionals, and individuals. This information is used to design and evaluate interventions to improve Indian health to the highest possible level, which is the goal of Indian Health Service (IHS). I will review some of the cancer prevention and control interventions being conducted in the Aberdeen Area Indian Health Service. The Aberdeen Area IHS serves 80,000 Indians who are members of seventeen tribal groups living in four states: North Dakota, South Dakota, Iowa, and Nebraska. It is an isolated area with severe transportation difficulties. Several years ago, I worked on a report for Congress called "Closing the Gap" or "Bridging the Gap," on the differential epidemiology in various areas of the Indian Health Service. We reported on a number of different health conditions, including cancer, utilizing age-adjusted mortality rates. Overall, Indian people are at less of a risk of dying from cancer than United States all races, but there are some areas, notably Alaska, Bemidji, Billings, and Aberdeen, where the rates of death from cancer are higher than the United States all races (figure 1). In Albuquerque, Phoenix, Navajo, Portland, and Oklahoma areas, the age-adjusted cancer mortality rates are considerably lower. In fact, the Navajo have about half the rate of death from cancer as the United States all races.