The study sought to (1) furnish data to be used in further language-error analyses and studies of causes of errors in language acquisition, (2) provide specific data for a basis in constructing pedagogical materials and proficiency tests to be used in teaching English to Mexican American children, and (3) determine whether bilingual or monolingual schooling affects the number and/or the patterning of errors. The sample consisted of 61 Mexican American children attending a monolingual school and 59 Mexican American children attending a bilingual school. The children were shown a silent movie and then asked to tell the story. Their answers were recorded on tape and transcribed. The deviations from standard English were described and categorized into errors in morphology, syntax, and vocabulary and counted as to their relative frequency in order to determine differences due to such independent variables as grade, sex, and type of schooling. Comparisons of frequency were based on comparisons made as to correct usage percentage within the 2 most frequent error categories and overall comparisons of all error frequency made as to number of errors per number of words. Major findings were (1) that deviations apparently were the result of the expected Spanish interference, the improper application of standard English rules, and the influence of nonstandard English dialects and (2) that children in the bilingual school did not differ significantly from those in the monolingual school with respect to frequency of deviations from standard English. (NQ)