The United States has experienced a significant increase in educational attainment since the 1970s. Young adults in school today are more likely than their parents to finish high school, attend college, and graduate from college. Yet, in California the share of working-age adults who do not have a high school diploma or certificate of General Educational Development (GED) has held steady at about 20 percent since the late 1970s. The share who have not finished ninth grade has stayed at about 10 percent since the early 1970s. This paper compares trends in the educational attainment of adults in California over the last three decades to trends in the rest of the nation. The paper then explores demographic factors that help account for the low level of education in California. The substantial share of California adults with low levels of education is of particular concern because the value of education in the labor market has increased substantially. The average earnings of workers with a high school degree or less have eroded while the average earnings for those with a bachelor's degree have grown. The evidence suggests that improving the education levels of low-earning workers will help to reduce the income gap in California, improve racial and ethnic disparities, reduce poverty, and improve child well-being. An appendix provides a data table showing: Adult Population with No High School Diploma or GED by California County, 2000. (Contains 5 figures, 5 tables, and 6 footnotes.) [This paper presents the testimony presented before the California State Assembly Select Committee on Adult Education, Assemblymember Carol Liu, Chair, July 29, 2003.]