The purpose of this article is to describe a study that examined the effects of a supplemental instructional method called sound boxes on the phoneme segmentation performance of a sample of preschoolers enrolled in a Head Start program. The sound box intervention was implemented using most to least prompting procedures as a way to scaffold children's acquisition, maintenance, and generalization of phonemes. Findings revealed that all children improved their performance on phoneme segmentation tasks during the implementation of the sound box intervention. Results also showed that all children were able to maintain their high phoneme segmentation performance levels after prompts were removed. Additionally, children were able to generalize segmenting a fair percentage of phonemes when they were presented within words that were not directly taught during intervention sessions. Limitations of the study and directions for future research as well as implications for Head Start educators who may be interested in implementing this intervention are provided. (author abstract)