The samples of towing rope disused after their usage in trawl fishing were collected from various fishing ports during the period from July, 1973 to July, 1976 and their properties were examined in relation to their fishing conditions. In this study, the results obtained are as follows: 1) Minimum ratio of strength (T/T0) allowable for the towing rope was nearly 30% in small sized fishing boats within 10 tons and nearly 50% in medium sized fishing boat. 2) Minimum ratio of diameter (D/D0) and weight per unit length (W/W0) of disused ropes were nearly 85% and 70%, respectively. 3) The larger the size of the net became, the larger the declining value of rope strength and the declining value was also large on rough fishing ground. 4) The declining values of strength of synthetic fiber ropes are generally smaller than that of manila hemp ropes. 5) Minimum values of the remaining tensile strengths of disused ropes in each tonnage of fishing boats are nearly in proportion to the tonnage of fishing boats. Where T0, T, D0, D, W0 and W are values before and after the usage in trawl fishing, respectively.