The tacticity dependence of the glass transition temperature (T-g) of a steric copolymer, such as poly(methyl methacrylate), composed of meso and racemic dyads, is discussed using T-g equations which is useful for ordinary copolymers. With the T-g values of isotactic and syndiotactic forms together with that of the heterotactic form newly determined therefrom, it was shown to predict satisfactorily the T-g value of a given steric copolymer from its triad data. In addition, it turned out that in a plot of T-g against dyad or (syndiotactic) triad fraction, a linear correlation can be expected only for steric copolymers containing negligible amounts of the heterotactic triad and, in general, the data are scattered due to different polymerization kinetics.