The experiment described in this report considers whether children who learn a second language will develop the same semantic system as monolingual children or whether their semantic system will be different because of linguistic or cultural interference, and also whether the bilingual child develops separate meaning systems for his two languages or whether he operates by means of a single system. The experiment compares the relative difficulty of certain semantic constructions in comprehension tests for two groups of young bilingual children: Spanish-English bilinguals and Navaho-English bilinguals. Details and results are provided. Findings indicate that bilingual children do not parallel monolingual children in patterns of difficulty of semantic categories. Categories not present in their first language are appreciably more difficult in relation to the other categories than for monolingual children. (Author/VM)