In their freshman year in college, Puerto Rican students take composition courses in both Spanish and English. Although the rhetorical structure of the final product, the composition, may respond to national writing styles in the two languages, studies show the composition process to be similar. Writing instructors in either language find similar problems in student compositions, regardless of the language code used. One of the difficulties students have in both languages is blocking, or apprehension about writing. Although some aspects of the composition process may be universal, we assumed that in bilingual writers the source of writing block depended on the language used. This article presents the results of a questionnaire designed to determine the sources of bilingual students' apprehension in writing by considering three groups of bilingual writers: graduate students in English, freshman English composition students, and freshman Spanish composition students. The results suggest some insights on the nature of blocking in a native language (Spanish) and a second language (English), which may then lead to ways of helping bilingual students to overcome blocking.