The present study was undertaken to measure and compare reading disabled and nondisabled readers" semantic and syntactic knowledge about derivational suffixes as a function of modality (reading versus listening) and as a function of the "neutrality" of the derivative (neutral versus nonneutral) . In the present study, neutrality refers to how straightforward and productive is the relationship between the root and derived form, with "completeness" qualifying as a neutral derivative and "completion" a nonneutral derivative. Two experimental tests were designed for the study. The Semantics test measured ability to extract lexical-semantic information from suffixed words, and the Syntax test measured knowledge regarding the part-of-speech contribution of derivational suffixes. In each test the target words were divided equally between neutral and nonneutral derivatives and between items that were either read or listened to. Participants included 20 sixth-grade reading disabled students (6RD), 20 fourthgrade normal readers (4N), and 20 sixth-grade normal readers (6N).In both the Semantics test and the Syntax test all groups scored better on neutral than on nonneutral derivatives while listening and reading, and the RD students were no more affected by neutrality than the nondisabled readers. In the Semantics test all groups scored better in listening than in reading, but the RD group showed the greatest oral-reading difference. The RD group also scored better in