This report examines how much undergraduates work while enrolled in postsecondary education for the academic year 1989-90. It specifically addresses types of institutions they attended, educational experiences, and the relationship of their education cost and financial aid to the amount of time they worked while enrolled. The report presents data from the 1989-90 National Postsecondary Student Aid Study in narrative and tabular forms. Results suggest that not only are most undergraduates working while they are enrolled, a substantial number are working full time. Other highlights include: (1) about 75 percent of all (full and part time) undergraduates worked at some time during 1989-90 of which 40 percent reported working full time at some time while enrolled; (2) among undergraduates enrolled full time for a full academic year, about 22 percent worked full time at some time during their enrollment; (3) undergraduates who attended private, for-profit institutions were much less likely to work while enrolled (61 percent); (4) undergraduates who worked while enrolled were employed for most of their enrollment; (5) most undergraduates held jobs in the areas of administrative support, service occupations, blue collar occupations, marketing, and as sales clerks; and (6) women were less likely to work full time while enrolled than men. Includes a glossary and technical notes. (Contains 12 references.) (JB)