||As computer assisted instruction (CAI) becomes increasingly sophisticated, its appeal as a viable method of literacy intervention with young children continues despite limited evidence of effectiveness. The present study sought to assess the impact of one such CAI program, Imagine Learning English (ILE), on both the receptive vocabulary and early literacy skills of 284 kindergarten students, including English language learners using a 2 x 2 cross-over research design over a period of a full school year. In each semester, students received either the ILE treatment or "other" treatment (integrated core curriculum including science, social studies, art, music, physical education). Specifically, the study sought to answer two questions: (a) How do the literacy skills of kindergarten students, including English language learners and monolingual children, who receive instruction using ILE compare with the literacy skills of kindergarten students who receive "other" classroom instruction; (b) how do the vocabulary skills of the same kindergarten students who receive instruction using ILE compare with the vocabulary skills of those who receive "other" classroom instruction? Results of the t-tests from this within-subjects design showed no treatment differences on outcome measures (PPVT-4 for receptive vocabulary and DIBELS Next for early literacy) between students when they participated in the ILE program and when they participated in "other" classroom activities, regardless of amount of time spent on this CAI program. These same results held true for English language learners for whom the program was originally designed. A strong period effect, however, was detected, with the treatment administered during period 1 (i.e., either ILE or "other" instruction) having a more positive effect on student language and literacy learning than the treatment that was administered during period 2. Possible explanations for this significant period effect are provided as well as cautions for the ongoing use of CAI programs such as ILE in early literacy education. Finally, recommendations for future research are set forth.