We evaluated and compared the strength of six extracorporeal slipknots used in laparoscopic surgery as measured with a tensiometer. Two multiple-throw laparoscopic square knots (intracorporeal two-turn flat square knot and extracorporeal sliding square knot) were used as controls. Each knot type was tied five times, and each type tied in random order by the same primary and assisting surgeons using a laparoscopic pelvic surgery training model. A one-way analysis of variance was performed to detect significant differences in knot strengths. The variability in strength for each knot type was determined using Tukey's multiple comparison test. A significant main effect for knot geometry was discovered (p <0.001). The mean knot strengths, measured in Newtons from strongest to weakest, were 4S knot 28.01 ± 11.45, fisherman's knot 22.45 ± 6.89, modified Roeder knot 19.86 ± 9.30, Roeder knot 15.77 ± 7.02, Weston knot 7.28 ± 7.96, and Duncan knot 6.55 ± 0.95. The mean knot strengths for the multiple-throw control square knots were intracorporeal two-turn flat square knot 41.21 ± 2.69 and extracorporeal sliding square knot 27.81 ± 16.27. The intracorporeal two-turn flat square knot (control) was significantly stronger (p <0.05) than all slipknots except the 4S and fisherman's knot. These are the strongest laparoscopic slipknots and are the only slipknots that compare in strength with multiple-throw square knots.