Root‐mean‐square end‐to‐end dimensions (r2)1/2 and molecular weights M have been determined from light scattering studies carried out on a series of fractions of poly‐(acrylic acid) in dioxane (θ point, 30°C.), on two polyisobutylene fractions in cyclohexane and in ethyl n‐caprylate (θ point, 22°C.), and on a single poly‐(methyl methacrylate) fraction in acetone. Intrinsic viscosities of the various polymers measured in these same solvents at the same temperature (30°C.) support the relationship [η] = Φ(r2)3/2/M, where Φ is a constant independent of molecular weight and solvent type and (according to the data herein reported) has the approximate value 2.2 × 1021. The θ points, representing the temperatures at which ideal behavior prevails, were determined for the two poor solvent–polymer systems by extrapolation of critical consolute temperatures to M = ∞. The intrinsic viscosity of poly‐(acrylic acid) in dioxane at 30°C. (the θ point) is given by [η] = 0.85 × 10−3M1/2; the value of the constant approximates those for nonpolar polymers. The influence of molecular weight heterogeneity on the fundamental relationship of the intrinsic viscosity to (r23/2/M) is analyzed, and it is shown that the true value of the universal parameter Φ will be greater than the apparent value deduced in the foregoing manner without correction for the heterogeneity of the polymer fraction. For a fraction possessing a relatively sharp distribution as denoted by 〈M〉w/〈M〉n = 1.15. the magnitude of this correction may be as high as 20%.