Due to recent interest in the use of elaborative contexts to enhance associative learning, the effectiveness of elaboration as an instructional technique in vocabulary development was evaluated with 107 educable mentally retarded children in three primary level classes. Ss were given vocabulary instruction under one of three instructional conditions: Relational (relational elaborations and thematic summary), Non-Relational (non-relational elaborations and non-relational summary), and Mixed (non-relational elaborations and thematic summary). Analyses of data related to vocabulary development and the utilization of instructional strategies indicated that all conditions demonstrated increases in "specific" vocabulary development and that the utilization of instructional strategies varied with the conditions. Evaluation of the three instructional conditions revealed that those receiving thematic summaries (the Relational and Mixed conditions) resulted in generally better performances. Results led to several suggestions for the development of elaboration-based vocabulary instruction for retarded children such as that concrete vocabulary words are easier to develop than are more abstract words. (Appendixes include a sample vocabulary lesson and the four tests used in the study. (LS)