The complexity of language of four, five, and six year old children was examined in a psycholinguistic study that attempted to differentiate the characteristics of sentences that were difficult for children to comprehend from those which were easy, and to discover whether children used a subject-verb-object (S-V-O) language strategy to interpret all of these sentences. A racially mixed group of 108 children participated in three sessions where they were asked to imitate or interpret (comprehend) approximately 100 sentences involving complex grammatical constructions. The five major parts of the study centered around five different sentence constructions: datives, genitives, comparison sentences, contrast sentences, and control sentences. Results indicated that sentence difficulty increased according to the deviation from the S-V-O word order and the greater number of concepts in a sentence, and decreased in the presence of semantic constraints on sentence interpretation. The presence of syntactic cues to structure failed to decrease sentence difficulty. (Eighteen tables are provided and appendixes include the scoring procedure for the imitation task, sample pictures used in the comprehension task, and a table of percent of correct responses for selected dative and genitive sentences.) (MAI)