Three different sliding knots were tested using five recently developed monofilament and multifilament suture materials. The resorbable materials were polyglactin-910 (Vicryl), polyglycolic-acid (Dexon-Plus), polyglyconate (Maxon), and polydioxanone (PDS), and the nonresorbable material was polypropylene (Prolene). For each type of sliding knot, three or five throws of suture were tested. Knot strength was determined by the loop holding capacity, which was defined as the strength at which the knot broke, or at which slippage in the knot amounted to more than 2 mm. When the three kinds of sliding knots were compared, identical sliding knots with identical throws around a single suture were found to be the most unreliable. Nonidentical and parallel sliding knots differed little with respect to knot reliability. Five-throw knots were generally stronger than three-throw knots. However, the effect of adding two extra throws to three-throw sliding knots was only significant if monofilament suture material was used. Comparison of the different suture materials revealed major differences in knot holding ability. These findings indicate that knot strength is dependent on both the type of knot and the type of suture material, and surgeons should be cognizant of these variables.