This study examined the effects of incremental rehearsal (IR) on letter sound expression for one kindergarten and one first grade English learner who were below district benchmark for letter sound fluency. A single-subject multiplebaseline design across sets of unknown letter sounds was used to evaluate the effect of IR on letter-sound expression and fluency. Although visual analysis of the data showed an increase in level and trend for the kindergarten participant, data were variable for the first grade participant who was referred for special education services during the intervention. Mean percentage of non-overlapping data (PND) was 94% for the kindergarten student and 98% for the first grade student. Although both learners made increases in letter sound expression and fluency, the intervention was 17 weeks in duration. Future research should examine both the effectiveness and efficiency of IR, as compared to other interventions, for increasing letter-sound knowledge of English learners.