Contemporary educational thought holds that one of the pivotal causes of inadequate school performance is the inability of schools to adequately staff classrooms with qualified teachers, especially in fields such as mathematics and science. Shortages of teachers, it is commonly believed, are at the root of these staffing problems, and these shortfalls are, in turn, primarily due to recent increases in teacher retirements and student enrollments. The objective of this study is to empirically reexamine the issue of mathematics and science teacher shortages and to evaluate the extent to which there is a supply-side deficit—a shortage—of new teachers in these particular fields. The data utilized in this investigation are from three sources—the Schools and Staffing Survey and its supplement, the Teacher Follow-Up Survey; the Integrated Postsecondary Educational Data System; and the Baccalaureate and Beyond Survey, all conducted by the National Center for Education Statistics. The data show that there are indeed widespread school staffing problems—that is, many schools experience difficulties filling their classrooms with qualified candidates, especially in the fields of math and science. But, contrary to conventional wisdom, the data also show that these school staffing problems are not solely, or even primarily, due to shortages in the sense that too few new mathematics and science teachers are produced each year. The data document that the new supply of mathematics and science teachers is more than sufficient to cover the losses of teachers due to retirement. For instance, in 2000 there were over two and half teachers in the new supply of math teachers for every one math teacher who retired that year. However, when preretirement teacher turnover is factored in, there is a much tighter balance between the new supply of mathematics and science teachers and losses. The data also shows that turnover varies greatly between different types of schools and these differences are tied to the characteristics and conditions of those schools. While it is true that teacher retirements are increasing, the overall volume of turnover accounted for by retirement is relatively minor when compared with that resulting from other causes, such as teacher job dissatisfaction and teachers seeking to pursue better jobs or other careers.