This study investigated the effects of computer use upon the computer literacy of preservice elementary teachers using two methods of instruction: computer assisted instruction in an earth science course and computer programming in a mathematics education course. Computer literacy was measured by the Minnesota Computer Literacy and Awareness Assessment (MCLAA). For each component of computer literacy, differences in group posttest scores were compared using an analysis of covariance with pretest scores used as the covariate. Pre- to posttest increases in scores for each group were also examined. The results indicated that the treatment given to the computer programming group had little or no effect upon the students' computer literacy, while the treatment given to the computer assisted instruction group had a significant effect upon the affective subscale of the MCLAA. A positive effect was also indicated on the cognitive subscale of the MCLAA. Thus, it appears that an effective method for improving preservice elementary teachers' computer literacy is to involve them in computer assisted instruction, possibly through a science course.