The main hypotheses addressed in the research were (1) whether imprecision in the phonological representations of lexical items underlies the impaired expressive naming abilities of disabled readers, and (2) whether weak verbal memory might mediate the relationship between naming and reading skills. From samples of 93 first graders and 67 fourth graders, extreme groups of good and poor readers were identified and compared on measures of receptive vocabulary, expressive naming, acceptability judgments for variants of object names, imitation and correction of naming errors by another speaker, pseudoword repetition, and long-term memory. Performance was generally better by older than younger students and by good than poor readers at each age, with little interaction between grade and reader group. The results indicated that for both good and poor readers, imprecise phonological knowledge, especially about long words, contributed to children's difficulties on all naming tasks. Memory differences, however, appeared to play only a minor role in explaining the strong association between naming and reading. (Contains 4 tables and 2 figures.)