The continuing crisis in the supply and demand for high school physics and chemistry teachers has been documented by a series of national surveys. There is a need, however, to augment these surveys with accurate longitudinal data which identifies the age-specific variables of science teacher survival rates, incoming number of new teachers, and the rate at which science teachers change age cohorts. These three variables were used in a five year longitudinal study of all the physics and chemistry teachers in Kansas to project the need for teachers in 1985 and in 1990. The study indicated that the teachers 40 years and older comprised 33.5% of the physics/ chemistry teacher population in 1979–1980 and the percentage will steadily increase to 60.8 by 1990. The high turnover rate of science teachers 29 years old and younger is also contributing to the shortage of qualified physics and chemistry teachers. The cohort component population projection method outlined in this study is recommended for use in other states to document the age specific characteristics of the science teacher population.