A molding composition is disclosed which comprises ultrahigh molecular weight polyethylene having an intrinsic viscosity of 10-30 dl/g at 135.degree. C. in decalin. Improved injection moldability is provided by the use of such polyethylene obtainable by a multi-stage polymerization reaction including at least the following two stages: (a) a first stage in which ethylene is polymerized using a specified composite catalyst in the absence of hydrogen of its presence at lower concentration to produce 50-99.5 weight parts of polyethylene having an intrinsic viscosity of 12-32 dl/g at 135.degree. C. in decalin; and (b) a second stage in which a fresh feed of ethylene is polymerized in the presence of hydrogen at higher concentration to produce 50-0.5 weight parts of polyethylene having an intrinsic viscosity of 0.1-5 dl/g at 135.degree. C. in decalin.