Sandholtz, Ringstaff, & Dwyer (1996) list five stages in the "evolution" of a teacher's capacity for computer-based instruction--entry, adoption, adaptation, appropriation and invention--which hereafter will be called the teacher's computer-based instructional evolution. In this study of approximately six hundred junior high school science and mathematics teachers in Taiwan who have integrated computing technology into their instruction, we correlated each teacher's stage of computer-based instructional evolution with factors, such as attitude toward computer-based instruction, belief in the effectiveness of such instruction, degree of technological practice in the classroom, the teacher's number of years of teaching experience (or "seniority"), and the teacher's school's ability to acquire technical and personnel resources (i.e. computer support and maintenance resources). We found, among other things, that the stage of computer-based instructional evolution and teaching seniority, two largely independent factors, both had a significant impact on the technical and personnel resources available in their schools. Also, we learned that "belief" in the effectiveness of computer-based instruction is the single biggest predictor of a teacher's successful practice of it in the classroom. Future research therefore needs to focus on how we can shape teachers' beliefs regarding computer-based learning in order to promote their instructional evolution. (Contains 7 tables and 2 figures.)