Blacks, Hispanics, and American Indians/Alaskan Natives are underrepresented in science and engineering fields. A comparison of race-ethnic differences at key transition points was undertaken to better inform education policy. National data on high school graduation, college enrollment, choice of major, college graduation, graduate school enrollment, and doctoral degrees were used to quantify the degree of underrepresentation at each level of education and the rate of transition to the next stage. Disparities are found at every level, and their impact is cumulative. For the most part, differences in graduation rates, rather than differential matriculation rates, make the largest contribution to the underrepresentation. The size, scope, and persistence of the disparities suggest that small-scale, narrowly targeted remediation will be insufficient.