This paper reports the results of research conducted in six classes (Form IV) with 205 students with a sample of 94 respondents. Data represent students' statements that describe (a) the role of Mathematics teachers in a computer-assisted instruction (CAI) environment and (b) effectiveness of CAI in Mathematics instruction. The results indicated that: majority of students incline towards constructivist Mathematics teaching-learning beliefs in a CAI environment; and CAI would encourage positive attitude towards Mathematics and instruction while negative attitudes are attributed to the design and development of CAI software among others. Prior student computer experience and skills are determinants for effectiveness of CAI in Mathematics instruction. The recommendations are that CAI catalyses a constructivist environment in Mathematics, and design and development impacts on its success in Mathematics instruction. (Contains 5 tables.)