The present study concentrated on the writing vocabulary of Mexican American children (grades 1-8) in order to answer the following questions: (1) Are there regional differences in the writing vocabulary of Mexican American Children? (2) Is one justified in translating directly from English into Spanish? (3) Is there a need for the development of specialized Mexican American language materials? (4) Can an informal reading inventory be formulated so that the grade level can be determined when the child reads in Spanish? Participating schools were selected from the roster of federally funded ESEA Title VII Bilingual Education Programs for 1975. Only those schools which indicated a majority of Mexican American speakers were included. Major focus was on Illinois, Texas and California. From the writing samples submitted, a vocabulary for each grade was randomly selected. Tabulation of vocabulary was done by computer: (1) according to frequency, (2) by grade and state, (3) to compare grade levels across state regions, and (4) to determine differences in frequency of use in words. A comparison was made between the 1976 Criscoe list of English vocabulary and the present Mexican American vocabulary study. Results are discussed in terms of applications to the development of bilingual education programs, both testing and methodology, specifically meeting the needs of the Mexican American student. (Author/CLK)