This paper presents an analysis of the distribution of phonological similarity relations among monosyllabic spoken words in English. It differs from classical analyses of phonological neighborhood density (e.g., Luce & Pisoni, 1998) by assuming that not all phonological neighbors are equal. Rather, it is assumed that the phonological lexicon has psycholinguistic structure. Accordingly, in addition to considering thenumber of phonological neighbors for any given word, it becomes important to consider thenature of these neighbors. If one type of neighbor is more dominant, neighborhood density effects may reflect levels of segmental representation other than the phoneme, particularly prior to literacy. Statistical analyses of the nature of phonological neighborhoods in terms ofrime neighbors (e.g.,hat/cat),consonant neighbors (e.g.,hat/hit), andlead neighbors (e.g.,hat/ham) were thus performed for all monosyllabic words in the Celex corpus (4,086 words). Our results show that most phonological neighbors are rime neighbors (e.g.,hat/cat) in English. Similar patterns were found when a corpus of words for which age-of-acquisition ratings were available was analyzed. The resultant database can be used as a tool for controlling and selecting stimuli when the role of lexical neighborhoods in phonological development and speech processing is examined.