Data from personal interviews with 705 Mexican American and 363 Anglo women during the 1979 U.S. Mexico Border Survey were analyzed to answer the question, To what extent do Mexican Americans and Anglos differ in having the number of children they want, when they want them? Mexican Americans had a significantly higher percentage of unwanted births than did Anglos. Much of this difference is related to the fact that Mexican Americans, when compared with Anglos, have completed fewer years of schooling and have incomes closer to the poverty threshold than do Anglos. Both Mexican Americans and Anglos had relatively moderate levels of planned births; thus, neither group is in full control of the number and timing of their births. Our results suggest that there is a substantial need for family planning services for Mexican Americans and Anglos in the Southwest.