Reduced sp. viscosity, light-scattering values, and Goode's J-value were detd. for mixts. of isotactic (I) and syndiotactic poly(Me methacrylate) (II) in CHCl3. Plots of these values vs. I-II ratios indicated that stereocomplexes appear not only at the 1:2 I-II ratio (shown by previous x-ray diffraction data), but also at a 2:1 I-II ratio. These 2 special interactions appear independently of the mol. wts. or tacticities of the isomers, and it is assumed that the stereocomplexes are not large structures.