Access to morphological structure during lexical processing has been established across a number of languages; however, it remains unclear which constituents are held as mental representations in the lexicon. The present study examined the auditory recognition of different noun types across 2 experiments. The critical manipulations were morphological complexity and the presence of a verbal derivation or nominalizing suffix form. Results showed that nominalizations, such as "explosion," were harder to classify as a noun but easier to classify as a word when compared with monomorphemic words with similar actionlike semantics, such as "avalanche." These findings support the claim that listeners decompose morphologically complex words into their constituent units during processing. More specifically, the results suggest that people hold representations of base morphemes in the lexicon.