A study investigated the relative effectiveness of three kinds of computer-mediated support for developing reading comprehension among learners of Arabic as a Foreign Language (AFL). Subjects were 24 first-year students of AFL at the college level. The students were given computer-assisted reading instruction at four levels of treatment: control (use of text only); access to a glossary; access to conjugations of selected verbs in the text; and access to background information about the text. Treatments were combined in a Greco-Roman square research design. Post-treatment reading comprehension was measured by an immediate recall protocol. Results suggest that of the three-computer-mediated reading supports used, the glossary was the primary contributor to enhancement of comprehension. Further research is recommended to address different populations, different languages and language skill levels, text length, text type, degree of student control over computer supports, and transfer of learning. (MSE)