In this 1-year experimental study of 254 students across 27 high-poverty preschool classrooms in an urban setting in the northeast, use of a technology-based prekindergarten literacy curriculum in addition to the district curriculum was compared with the use of the district curriculum alone. Results indicated no main effects for the experimental curriculum. Following the initial analyses, fidelity of implementation in the experimental classrooms was examined and results indicated that children in classrooms rated as having high fidelity of implementation significantly outperformed low-implementing classrooms on two important phonological awareness measures. This trend favoring high-implementing classrooms was also evident on measures of letter-name knowledge, and beginning sounds. These findings suggest that program implementation may be a significant variable when examining the potential effects of literacy curricula on learning outcomes for young at-risk children. (Contains 9 tables and 1 figure.)