This paper discusses the role of high school chemistry teachers' beliefs in implementing computer visualization software to teach atomic and molecular structure from a quantum mechanical perspective. The informants in this study were four high school chemistry teachers with comparable academic and professional backgrounds. These teachers received training on the use of software applications and the underlying scientific concepts, expressed commitment to using the software with their classes, and taught students at the same academic level. All of the participants used the software to teach concepts related to atomic and molecular structure. Their instructional approaches ranged from superficial fact-based activities to in-depth student investigations and presentations. Evidence suggests that the teachers' beliefs and personal goals shaped their decisions on how to use the software. Beliefs related to the teachers' views about how students learn and their own roles as teachers had the greatest influence on pedagogical decisions. This paper describes the instructional strategies and the implied and stated rationales of participating teachers, and develops a theory of a relationship between teachers' beliefs and practices when implementing interactive computer models. (Contains 56 references.) (Author/WRM)