The purpose of this study was to characterize and compare 64 elementary science teachers' computer simulation use prior to and following professional development (PD) aligned with Innovation Adoption Theory. The PD highlighted computer simulation affordances that elementary teachers might find particularly useful. Qualitative and quantitative data, including perceptions surveys, participant interviews, Quarterly Lesson Reports, and videotaped lessons, were analyzed to identify changes in participants' computer simulation use. Variables that hindered or promoted instructional computer simulation use were also identified. There was a significant increase in the number of participants that used computer simulations pre- (17%) to post- (52%) professional development. Implementation patterns following the PD demonstrated participants consciously took advantage of simulations to address appropriate content and for inquiry-based instruction. The primary barrier to instructional computer simulation use was participants' belief that computer simulations are most effective when used by students independently or in small groups. Findings illuminate Innovation Adoption Theory's potential and limitations for use when designing educational technology professional development. A modified six-stage adoption model is recommended to address participants' beliefs and has implications for how pre-service and in-service education is implemented.