Noting that the quality of child care and early education available to lower-income families has received considerable attention over the past decade, this study explored variability in the quality of California day care centers and preschools. Participating in the study were 170 centers and preschools situated among 20 California zip codes, clustered in three counties: Los Angeles, San Francisco, and Santa Clara. All the zip codes selected contained significant concentrations of lower-income families. Findings indicated that the majority of centers displayed high levels of quality along structural measures, such as class size, the ratio of children per adult, and staff education levels. About one in six failed to meet recommended quality standards. Some quality indicators were slightly lower for centers located in communities with less supply, possibly due to directors' attempts to accommodate greater family demand for enrollment slots. Center quality was not consistently influenced by community conditions such as poverty levels, ethnic composition, or maternal employment rates. Quality was higher among centers receiving stronger flows of public subsidies. Analysis of findings centered around the success of state agencies in building high quality among centers in lower-income communities as well as the policy challenges that remain. Maps indicating the sampled communities by zip code are appended. (Contains 14 references.) (KB)