This paper summarizes the results of a study of the impact of immigration on California, particularly in Los Angeles County. Of the 1.7 million foreign-born persons in Los Angeles County in 1980, 950,000 (or 57 percent) came to the United States after 1970. Mexican immigrants comprise almost one-half of the total of recent arrivals. They tend to be below the native population in educational attainment and occupational status. In 1980 two-thirds of the adult Mexican immigrant population in Los Angeles had less than a ninth-grade education, and five out of six experienced workers held blue-collar jobs--mostly as operatives and laborers. One-half of recent Mexican immigrant workers in Los Angeles were employed in manufacturing, and Mexican immigrants accounted for between one-third and one-half of all employment in industries such as textiles, apparel, lumber and wood, and furniture and fixtures. The influx of Mexicans to southern California during the 1970s does not appear to have increased the aggregate level of unemployment among blacks. Some of the slower-than-average wage growth in low-wage manufacturing in Los Angeles during that time is attributable to the high proportions of Mexican immigrants in these industries, but the impact of Mexican immigrants on the wages paid to non-Hispanics in semi-skilled and skilled occupations appears to be negligible. A list of references and related titles is included. (Author/PS)