Inspection is a fundamental means of achieving software usability. Past research showed that during usability inspection the success rate (percentage of problems detected) of each individual inspector was rather low. We developed perspective-based usability inspection, which divides the large variety of usability issues along different perspectives and focuses each inspection session on one perspective. We conducted a controlled experiment to study its effectiveness, using a post-test only control group experimental design, with 24 professionals as subjects. The control group used heuristic evaluation, which is the most popular technique for usability inspection. The experimental results are that 1) for usability problems covered by each perspective, the inspectors using that perspective had higher success rate than others; 2) for all usability problems, perspective inspectors had higher average success rate than heuristic inspectors; 3) for all usability problems, the union of three perspective inspectors (with one from each perspective) had higher average success rate than the union of three heuristic inspectors.