Characteristics that would tend to place Mexican immigrants in direct competition with native workers for jobs at the bottom of the wage and skill hierarchy are their numbers, their largely undocumented status, low education and skill levels, and poor English-speaking ability. Using regression analysis, 1980 Census data were analyzed to determine whether concentrations of Hispanics in the labor market increased unemployment in the Los Angeles metropolitan area. Analyses found no evidence of an immigration-induced increase in unemployment, even with Los Angeles' high concentration of undocumented Mexican immigrants. Significantly, Black workers, who potentially may be the group most seriously affected by a surge of low-wage immigrants, showed a general upgrading in their occupational status. There were indications, however, that this immigration may have altered the pattern of internal migration to the region. Evidence suggested that the rate of low-wage workers migrating to California from other parts of the country had declined while the flow of immigrants from Mexico had increased; and the rate of out-migration had risen steadily. Mexican immigrants who came to California during the 1970s may have served as labor market complements to skilled internal in-migrants and as substitutes for less-skilled workers. (JMM)