Epidemiological relationships were studied between adolescent (ages 15 to 24 years) suicide rates and population shifts among adolescents. Suicide rates among adolescents tripled from 1956 to 1977 and have subsequently leveled off. Increases (and decreases) in adolescent suicide rates corresponded to increases (and decreases, respectively) in the proportion of adolescents in the United States. Opposite trends have been found among older age groups. Projected population fluctuations were used to predict trends in adolescent suicide rates to the year 2000: the current decrease in rates is predicted to continue until the mid-1990s. Recent data indicating a decrease in adolescent suicide rates tend to support the population model hypothesis. The data suggest that demographic variables may be of explanatory and predictive use in understanding the epidemiological trends of suicide. Early intervention and prevention strategies emerge from this model, and various social, public health, and research implications exist. However, the results must be viewed with caution because of the methodological problems inherent in using national mortality data, the possibility that other variables may account for the observed relationships, and the length of time required to test such prospective epidemiological propositions.