Demographic factors that will determine enrollment potential and service needs for California's segments of postsecondary education over the next 15 years are examined. Attention is directed to total population, age distribution, race composition, geographic distribution, and socioeconomic status. To provide some indication of changes that might occur in postsecondary education, information is provided on shifts in the composition and the progression of grade cohorts through the school system from kindergarten to high school graduation. Recent trends in college and university enrollments in the United States and California are reviewed to identify dimensions of participation that will most strongly affect future enrollment potential. Included are differences in participation for California's counties and eight metropolitan regions. Differences in participation for the University of California, California State University, and the community colleges are also identified with a focus on ethnic composition, age distribution, family income, and parental educational attainment. The California Postsecondary Education Commission's computer-based model for simulating the effects on enrollment potential of various potential changes in demographics is also described. (SW)