The ability of 31 institutionalized trainable mentally retarded mongoloid and nonmongoloid subjects (mean IQ=27.5) to comprehend and imitate verbally presented sentences of varying levels of grammatical complexity was examined. Eight stimulus sentences were spoken for four pairs of pictures, simple declarative or kernel, negative, passive, and negative passive. Subjects were asked to select one of a pair of pictures for each sentence and then to repeat the sentences. They correctly comprehended kernel sentences significantly more often than other kinds of sentences. Among nonmongoloid subjects, imitation of sentences to which one optional transformation had been applied was significantly better than imitation of sentences modified by two potential transformations. Chronological age was significantly associated with imitation ability in nonmongoloids (p .04); IQ and imitation ability were significantly associated in mongoloids (p .05), indicating that the ability to store verbal material for immediate recall is associated with general intellectual or cognitive abilities. (Author/RJ)