Twelve kinds of knots commonly used in surgical practice were tested with respect to holding power, expressed as loop-holding capacity. Two synthetic absorbable suture materials were used: nonlubricated polyglycolic acid (Dexon-S) and lubricated polyglactin-910 (Vicryl). The knots were selected on the basis of an inquiry among 25 experienced gynecologists, well known in the field of gynecologic surgery. Five of the 12 knots were sliding knots, four were square knots, and the remaining three were surgical knots. Sliding knots were routinely used by 20 of the 25 respondents (80%). The loop-holding capacity of various knots differed widely, ranging from 5 to 65% of the tensile strength of the unknotted thread. Square knots were stronger than sliding knots, and, in general, the holding power could be increased by adding extra throws to the knot. The findings revealed that the properties of various knots used in surgical practice differ considerably. Therefore, sufficient knowledge about knot configuration and knot strength seems to be an important and basic aspect of surgical handicraft.