The family size of the constituents of compound words, or the number of compounds sharing the constituents, has been shown to affect adults' access to compound words in the mental lexicon. The present study was designed to see if family size would affect children's segmentation of compounds. Twenty-five English-speaking children between 3;7 and 5;9 were asked to explain the meaning of existing compounds with constituents of varying family size to an alien puppet. The results showed that children were more likely to mention the modifier of compounds if they came from large constituent families than if they came from small constituent families. Other variables were also shown to have some, but smaller effects on children's parsing, including the frequency of the constituent words and the compounds, whether the compounds were already known, and age. These results suggest that children's segmentation of compounds might be facilitated by analogy with other compounds already in their vocabularies.