This national study of doctoral students examined various components of human capital and their effects upon doctoral students' experiences and achievement. Participants were 13,160 graduate students in 11 fields from 21 universities, including all African American, Asian American, Hispanic American, and Native American students, 300 white students, and one-half of all international students in the selected fields. Students completed the Survey of Doctoral Student Experiences, Performance, and Achievement, which examined demographic differences, backgrounds, finances, experiences, progress, and performance, and the relationship of these variables to the quality of students' experiences and performance in doctoral programs. Results indicated clear human capital differences between major fields and among racial groups. Engineering students in each ethnic group had more human capital than science/mathematics students. They had parents with higher levels of education and occupation, had attended the most selective colleges and universities, had higher college grades and test scores, and had had more work experience before entering doctoral programs. For the four racial and ethic groups, white and Asian students had the greatest, and African Americans had the least, amount of human capital and research productivity. Doctoral grade point average was of little use for discriminating by major field or race; research productivity yielded greater discrimination. (Contains 11 tables.) (SM)