Linear polyethylene was blended with an adhesive, an improving agent and polytetrafluoroethylene (I) (about 0.7, 8 and 1.4% by mass, resp.), formed by casting as a film and studied for resistance to puncture. The increasing of adhesive and improving agent contents resulted in increasing the film resistance to puncture. The addn. of larger amt. of I resulted in deterioration of the film strength.