This report examines the participation of older undergraduates, above age 24, in postsecondary education using data from the 1989-90 National Postsecondary Student Aid Study (NPSAS:90) and the 1990-92 Beginning Postsecondary Student Longitudinal Study (BPS:90/92). It profiles older undergraduates and compares them with younger undergraduates with regard to demographic and socioeconomic characteristics, enrollment patterns, how they combine working with studying, and the types, sources, and amounts of financial aid they receive. It describes the participation of selected subgroups of older undergraduates including those employed full time, those enrolled full time, those enrolled less than half time, those assisted by their employers, those without high school diplomas, and single parents. Examination of persistence and attainment among older students who enrolled in postsecondary education for the first time in 1989-90 covers combining working and studying, participation in campus activities and programs, and controlling factors related to persistence. Some of the report's highlights include: (1) in 1989-90, 42 percent of all undergraduates were 24 years or older; (2) a majority of older undergraduates were married and had dependents other than a spouse; (3) 59 percent of older undergraduates attended a public less-than-4-year institution (compared with 33 percent of younger undergraduates). Appendixes contain a glossary, technical notes, and information on methodology. (JB)