Abstract: Random ethylene-propylene copolymers with statistically distributed long C₃-sequen-ces should have thermoplastic elastomeric properties as a result of the dual features in its molecular structure, contributing both to elasticity and PP higher temperature plasticity. In this work δ-TiCl₃-Et₂AlCl catalyst was used in an attempt to obtain E-P copolymers with isotactic PP sequences for the benefit of higher strength.The effect was studied of [Ti],[Al]/[Ti], polymerization temperature and duration, and monomer composition on the polymerization yield, [η], MWD and copolymer composition. Structure of the copolymers was proved by heptane-extraction, dynamic mechanical properties,IR spectra and x-ray diffraction studies. Crystallinity is the prime factor responsible for their strength, to which [η] also contribates. High C₃ E-P copolymers are characterized by high crystallinity, strength and hardness and high elongation. A sample with C₃=79.8 mol% had a 300% modulus of 102 kg/cm² and a breaking strength of 135 kg/cm².