A longitudinal study was conducted to determine the short-term (2-year), intermediate (5-year), and long-term (10-year) impact of earning a high school equivalency diploma by taking the General Educational Development (GED) Tests in Iowa. The random sample of 2,500 GED graduates was drawn from each time cohort (individuals who had passed the GED Tests in 1980, 1985, and 1988) for a total sample of 7,500. A 6-page, 40-item follow-up survey was mailed in spring 1991; 1,597 returns were received, with similar response rates for the 3 follow-up time cohorts. Findings indicated that between just prior to passing the GED Tests and 1990, respondents reported substantial and statistically significant gains in employment, hours worked per week, job skill level, job satisfaction, personal income, reduction in welfare, job quality, property acquisition, and personal savings. The gains in hours worked per week were greatest between 2 and 5 years after passing the GED and then they leveled off between 5 and 10 years. The reported gains in job skills, job satisfaction, personal income, savings and indices of job quality, and economic benefits increased steadily over time. The overwhelming majority of GED graduates who enrolled in the adult basic education (ABE) program reported that attending ABE classes had helped them acquire the requisite knowledge to pass the GED Tests. (Appendixes, amounting to approximately one-half the report, include 24 references, information on the instruments employed in the study, qualitative comments, and descriptive statistics.) (YLB)