The study reported here compares the performance on a mental ability test of children in grades two and three from homes in which English is the language spoken with those from homes in which Spanish is the language used. During the Spring semester, the InterAmerican Tests of General Ability, Level Two, and their Spanish parallel, were administered in a number of central and southern California elementary schools. The research design provided that pupils be selected for the tests "to represent fairly (1) the entire population of school children from homes in which English is the major language (English speaking), and (2) the entire population of children from homes in which Spanish is the major language (Spanish speaking)," with about an equal number of boys and girls. Socioeconomic levels of the subjects were to be reported on the basis of parents' occupation. The students were selected from the schools or classes which represented the three socioeconomic levels, by systematic choice from an alphabetical list. The InterAmerican Tests of General Ability at Level Two comprise four subtests: Oral Vocabulary, Number, Classification, and Analogies. No reading is required of the testees; all items are in pictorial, figural, or numerical form. At both grades two and three, it was found that English-speaking children attained higher scores than Spanish-speaking children for total score as well as for each of the subtests. When the subtests are compared it becomes evident that the superiority of the English-speaking children is most marked on the Vocabulary and Number subtests. (Author/JM)