The proposed project advances a new approach to measuring and analyzing the demographic parameters of the Mexican-American population through the use of vital statistics data. Census procedures will be replicated to identify the Mexican-American population experiencing vital events in California. Comparative demographic analysis will examine levels, characteristics, and trends in the demographic performance of the Spanish-surnamed population in relation to those of other groups. Answers will be sought to such questions as the significance of the recent decline in Spanish-surnamed fertility, the degree to which fertility differentials can be ascribed to socio- economic differentials, and the health implications of the group's age and cause pattern of mortality. The cohesiveness of the Mexican- American community and the rigidity of the social boundaries around it will be assessed by means of cross-sectional and longitudinal studies of family formation and dissolution. The degree of out-marriage from the Spanish-surnamed group will be emphasized as an indicator of assimilation and the persistence of Mexican cultural traditions.