The security of several types of laparoscopic and open knots and varying suture materials was tested in an attempt to improve suture and knot selection for advanced laparoscopic procedures. Six different types of knots and five suture materials were tested. All sutures were of 2-0 size, and laparoscopic knots were tied using a pelvic trainer. A typical number of square throws was used for each suture. Stress was gradually applied by withdrawing the ends of a manual digital tensiometer until either the knot slipped or the suture parted. The maximum stress withstood by the knot-suture complex was recorded, as was whether the knot was secure (i.e., whether the knot held until the suture broke). The data were analyzed using analysis of variance to compare the knot security of the various knot types and the different sutures using a given knot. No significant difference was found in security or stress resistance between laparoscopic square and open square knots or in the Dacron, polypropylene, and expand polytetrafluoroethylene (ePTFE) extracorporeal and intracorporeal knots, with the exception of ePTFE intracorporeal knots, which were significantly less secure (p = 0.028). Silk suture was significantly less secure than all the other sutures tested for all knots tested (p < 0.0001). The Roeder's and Fisherman's knots were the least secure of all laparoscopic knots in all sutures tested (p < 0.0001), with the exception of polyglactin tied with a fisherman's knot, which was as secure as the extracorporeal and intracorporeal polyglactin knots. These experiments showed laparoscopic square knots to be as secure as open square knots; removing the operating finger from the knot does not seem to affect the security of a well-tied square knot. Furthermore, of the permanent sutures tested, there was no substantive difference in the security of laparoscopic intracorporeally and extracorporeally tied knots, except that ePTFE was more secure when tied with extracorporeal throws. Our data also suggest that silk is not as secure as other permanent suture materials.