The purpose of this study was to examine changes in nutrition knowledge, intakes, attitudes, and behaviors as well as health status of 22 female adolescent runners. Subjects completed questionnaires, interviews, and dietary analyses twice over a 3-year period. Over this time they experienced physical growth and improved athletic performance. Although their mean score on a test of basic and sports nutrition knowledge remained stable at 67%, after 3 years more runners correctly responded to statements about carbohydrate and fat. However, fewer responded correctly to statements regarding fluid intake and skipping meals. Although runners increased the percentage of calories consumed as carbohydrates, they significantly decreased their mean energy intake, thus lowering carbohydrate intake. They significantly lowered protein, calcium, potassium, and sodium intakes. The incidence of possible eating disorders increased, as did stress fractures. Over 3 years, nutrition knowledge did not improve, the quality of dietary intakes decreased, incidence of eating disorders and stress fractures increased, and menstrual irregularities remained high.