Purpose: To examine how adults with dyslexia versus adults with typical reading form lexical representations during pseudoword learning. Method: Twenty adults with dyslexia and 20 adults with typical reading learned meanings, spellings, and pronunciations of 16 pictured pseudowords, (half with regular and half with irregular grapheme-phoneme correspondences) presented first in 1 modality (spoken or written) and then the 2nd modality. Dependent measures included picture naming and identification, episodic recognition, a rhyme task, and a categorization task. Results: Adults with dyslexia learned pseudowords more slowly than those with typical reading and were disproportionately poor in learning irregularly spelled pseudowords after changing from written to spoken modality. Adults with dyslexia recognized fewer pseudoword forms than adults with typical reading and verified fewer pseudoword rhymes. Adults with typical reading were more accurate with categorizing regular versus irregular pseudowords. Adults with dyslexia did not show this regularity advantage. Conclusions: Adults with dyslexia, compared with adults with typical reading, failed to (a) encode and retrieve detailed information about pseudoword forms, (b) efficiently form cross-modal associations between written and spoken encounters with pseudowords, and (c) effectively modify their representations following the change in modality. The authors discuss implications relative to common theories of dyslexia. (Contains 3 tables and 1 figure.)