Over the past two decades peoples of Hispanic descent have had an increasing impact on the ethnic, socioeconomic, and demographic features of the U.S. population. This book draws together evidence from the 1980 census, earlier censuses, and other sources to portray the changing position of Hispanics in a complex and multiethnic society. Roughly 86% of the Hispanic population consists of persons of Mexican, Puerto Rican, Cuban, or Central or South American origins, while the remaining 14%--frequently denoted "Other Hispanics"--consists of persons of Caribbean or Spanish origins, as well as native-born citizens descended from the Spanish settlers of the Southwest. The great heterogeneity of these groups makes it impossible to speak of a single "Hispanic population." The book contains 10 chapters and an epilogue. Chapter 1 theorizes on the meaning of Hispanic ethnicity, focusing on the conception of ethnicity as a process. Chapter 2 discusses data sources and changes in enumeration practices and definitions. The remaining chapters are organized around specific demographic and socioeconomic factors, an approach that focuses analysis on: (1) the themes of persistence and change; (2) patterns of diversity and uniformity among the various Hispanic origin groups; and (3) patterns of convergence or divergence between Hispanic groups and the non-Hispanic White majority. Topics beginning with the third chapter are: general demographic profile; immigration; geographic distribution, internal migration, and residential segregation; marriage, family, and household; fertility patterns; educational attainment and school enrollment; labor force participation and unemployment; and income and poverty rates. This book contains 291 references, 104 data tables, 39 graphs and maps, and name and subject indexes. (SV)