New surgical suture materials with varying knot properties are continuously introduced. A method to measure and describe the knot properties of these different fibres is wanted but, today, no generally accepted method is available. During recent years, however, two different methods, the single strand and the loop technique, have been introduced. In the present report these two methods are compared. It is shown that the values obtained with the loop technique were influenced by other factors than the knot properties of the material while the single strand technique allowed an elective estimation of the knot properties of a fibre.