Living propylene polymerizations were performed with various metallocene catalyst (Mt = Zr and Hf)/cocatalyst (organoborane)/trialkylaluminium systems at low temperatures, i.e. Cp2ZrR2 (CP = cyclopentadienyl, R = Me and Cl)/B(C6F5)(3)/AlR'(3) (R' = octyl and iso-butyl) at -78degreesC, Cp2HfMe2/B(C6F5)(3)/AlOct(3) at -50degreesC and Cp-2*HfMe2 (Cp* = pentamethylcyclopentadienyl)/B(C6F5)(3)/AlOCt(3) at -78degreesC. TheCp(2)*HfMe2 system showed a considerably higher propagation rate than the Cp2ZrR2 or Cp2HfMe2-based systems. With the above metallocene catalyst systems, atactic polypropylene-(ethylene-co-propylene) (ataPP/EP) block copolymers were prepared by the addition of ethylene monomer during the living polymerization of propylene at low temperature. By the addition of ethylene, the M-n for the resultant copolymer showed a higher value than that of corresponding homopolypropylene while retaining the narrow molecular weight distribution. By the transmission electron microscopy (TEM) analysis, a microphase-separated morphology with ca. 50-100nm dimension was observed in an iso-PP/PP-block-EP blend.