This study examined the phonological neighborhood characteristics (frequency, density, and neighborhood frequency) of 138 malapropisms. Malapropisms are whole word substitutions that are phonologically, but not semantically, related. A statistical analysis of a speech error corpus suggests that neighborhood density and word frequency differentially affected the number of malapropisms. Specifically, a greater number of malapropisms were found among high frequency words with dense neighborhoods than with sparse neighborhoods. Exactly the opposite pattern was found among low frequency words. That is, more errors were found among low frequency words with sparse neighborhoods than with dense neighborhoods. More malapropisms resided in low frequency neighborhoods than in high. The average word frequency, average neighborhood density, and average neighborhood frequency of the malapropisms were significantly lower than the same averages computed from randomly sampled control words. Finally, more target words were replaced by error words that had relatively higher frequency than by error words that had relatively lower frequency. The implications of these findings for models of lexical representation and processing are discussed.