This report focuses on public opinion in Southern California, a region with one of the largest immigration populations in the country, in comparison to other regions and whether or not it changed over time. Additionally, it analyzes the determinants of attitudes towards immigration in the region. Findings include that Californians are generally more accepting of immigrants in comparison to other regions, and they have become generally more tolerant than in the past. The report recommends that immigration policy reform take into consideration the complexity of public opinions about immigration (e.g. support for one policy does not guarantee support for another), and that policies should be devised after a discussion about the costs and benefits of immigration since policy is already very cost-based so as to maintain objectivity.