Sixteen Head Start classrooms, involving 128 children, were randomly assigned to three approaches for augmenting early literacy instruction: (a) instruction in phoneme segmentation, blending, and letter-sound relationships, (b) rhyming instruction and (c) vocabulary instruction. The phoneme segmentation approach was more effective in promoting phoneme segmentation skill. Existing research suggests that phoneme segmentation skill is a better predictor of early progress in learning to read than rhyming skill or vocabulary knowledge. Thus, the results suggest that instruction emphasising phoneme segmentation is not only more likely to promote phoneme segmentation skill, but also more likely to promote future reading ability than rhyming or vocabulary activities, even for highly disadvantaged children as young as 4 years old.