The purpose of this investigation was to determine the influence of knot configuration and tying technique on the mechanical performance of surgical sutures. Multifilament and monofilament nylon sutures were selected for this evaluation because they are commonly used in wound closure. The mechanical performance of these sutures was judged by the following parameters: knot breakage force, configuration of secure knots, and knot run down force. During each test, tension was applied at either rapid or slow rates, which correlates with the physician's speed of tying knots. On the basis of these mechanical performance tests, four throw square (1 = 1 = 1 =1) knots and five throw square (1 = 1 = 1 = 1 = 1) knots are recommended for monofilament nylon and multifilament nylon sutures, respectively, in which the speed of application of forces to the knots is relatively slow. Because these tests can easily be replicated in any laboratory, manufacturers now have a scientific basis for recommending specific tying techniques for their surgical sutures.