Sensory impairment in the cutaneous distribution of the saphenous nerve was measured in 30 patients after bilateral stripping of the long saphenous vein. The vein was stripped upwards in one leg and downwards in the other. Three months after operation a significantly greater incidence of sensory loss was found in those legs in which the vein was stripped upwards (13 out of 26) compared with those which had been stripped downwards (6 out of 26).We recommend that the long saphenous vein should be stripped downwards.