A study examined the effectiveness of semantic mapping instruction as a technique for increasing vocabulary. Subjects, 38 fourth grade students in two classrooms, were divided into experimental and control groups. Both groups were pretested for their knowledge of selected words taken from the Scott, Foresman Reading Program, Grade Four. The control sample was then taught vocabulary using the traditional dictionary technique suggested in the basal manual, and the experimental group was taught semantic mapping, involving the development of a network of semantic categories by the students using their existing knowledge of vocabulary. Posttest results at the end of the six-week period indicated no statistically significant difference between the two groups. However, the experimental group exhibited a great enough gain over the control sample to warrant replication of the study over a greater period of time. (Tables of results and references are included, and appendixes contain the vocabulary test, the list of target words, and the raw scores for the pretest and posttest.) (HTH)