A study examined the impact of oral language competence on the writing behavior of secondary students of English as a second language (ESL). Samples of student writing in both the native Spanish and English were analyzed along five dimensions (topic of the composition, internal organization of thoughts, conveying meaning, sentence construction, and mechanics) and by two quantitative measures (number of main independent clauses and total words per composition). The profile describing the writing performance of each student was then compared to his oral proficiency test score. It was found that the greatest overall difficulty with the ESL writing was lack of vocabulary. No composition received full credit on any of the five dimensions studied. Most students were able to group sentences into paragraphs, but still needed help on organizational strategies such as logical beginnings or introductions and conclusions. Some students showed parallel abilities in both native and second languages, but others showed unequal competence in the two languages. Oral language development could have an effect on writing behavior, but oral language proficiency scores may not indicate what to expect of the students' composing behavior. More prewriting activities and increased class time on each topic are recommended. (MSE)