Communication: The mechanical properties and orientation behavior of atactic poly(methyl methacrylate) films cast from acetone (A-aPMMA films) and chloroform (C-aPMMA films), with subsequent sub-T-g annealing, have been studied. The formation of stereocomplex in sub-T-g-annealed A-aPMMA films and C-aPMMA films was demonstrated by means of differential scanning calorimetry. Stereocomplex in A-aPMMA films is more pronounced than in C-aPMMA films at each annealing temperature. It is proposed that stereocomplex formation can process at temperature below T-g, leading to enhanced yield stress and higher orientation.