This study investigated the use of tools and design features as employed in a problem-based learning (PBL) environment and their effectiveness on seventh grade students' learning of science concepts. Specifically, the study examined: (1) the effect of the computer-supported PBL environment on the achievement of middle school students; (2) the effect of the computer-based PBL environment on middle school students' attitudes toward science; and (3) the relationship between students' math or reading ability and their achievement in the PBL environment. Dependent measures were achievement, degree and frequency of access to the tools/features, and attitude toward learning science. The treatment consisted of three groups: computer-supported PBL environment, paper-based PBL, and a control group. Results indicated that: both the groups that used the computer-supported and paper-based PBL significantly improved their achievement scores, while the increase for the control group was not significant; there was no significant difference between the computer-supported and paper groups; students' reading ability is a better predictor for students' achievement in a PBL environment than their math ability; and students' attitude toward learning science was not affected by the introduction of PBL. Two tables and a graph present data. Contains 14 references. (DLS)