This paper contains a meta-analysis of studies on overeducation and undereducation in the labor market. It is found that of the four different definitions of overeducation distinguished in the literature, only the one based on variation in years of education within occupational groups appears to yield significantly lower-than-average rates of overeducation. The average rate of undereducation in the labor market depends on the definition of the undereducation variable. There is no indication that mismatches between education supplied and education required for the job have increased significantly in the past 20 years. The labor force growth rate has a positive effect on the incidence of overeducation, while the unemployment rate has a negative effect on the rate of return to education. (C) 2000 Elsevier Science Ltd. All rights reserved.