Empirical research on the supply and demand of math and science teachers finds some surprising results. The employment of qualified math and science teachers has more than kept pace with the demand, and most schools find qualified teachers for those positions. However, about a third of public schools--particularly high-poverty, high-minority, and urban public schools--have difficulty finding math and science teachers. This is caused by the high rates of teacher turnover in these schools. (Contains 3 figures.)