The construct validity of a surgical bench-top simulator with built-in computer acquired assessments was examined. It features two parallel elastic tubes instrumented with flexion sensors that simulate the walls of a wound. Participants from three groups (9 novices, 7 intermediates, 9 experts) performed 10 two-handed, double square knots. The peak tensions at the initiation of the first knot, the completion of the first knot and the completion of the second knot, as well as measures of movement economy indicated technical performance. Product quality was indicated by knot stability defined as the amount of slippage of the knot under the tension. There were significant differences between experts and novices for peak tension on first knot (p=.03), movement economy (p=.02), and knot stability (p=.002). The results support the construct validity of these objective measures.