A self-tightening knot for tying tubular casings such as sausage casings, cheese casings, or the like, comprises a doubled end portion of a flexible strand having a pair of substantially parallel strand segments and an end loop, a pair of overlapping bights in said end portion, and at least a pair of turns in said end portion between said bights. The end loop passes through said turns and holds the overlapping bights under at least one of said turns when the end loop is drawn taut and the knot is secured.