Data from the literature on four dilute solution properties-radius of gyration, second virial coefficient, intrinsic viscosity, and diffusion coefficient-were analyzed for linear flexible-chain polymers of several species in both thermodynamically good solvents and Theta solvents. Each property was expressed as an effective coil radius, and the ratio of good to Theta solvent radius, the excluded volume expansion factor, was examined over a wide range of chain lengths. The expansion factor, near unity for short chains, crosses over to a power law dependence on chain length for long chains. All data beyond the oligomeric range collapsed to a master curve for each property by a simple rescaling of the chain lengths. The crossovers for these curves are more abrupt than those predicted by the classical theories of polymer solutions. The excluded volume per monomeric unit, obtained by matching experiment and prediction in the power law region, is generally much smaller than the hard sphere prediction in even the best of good solvents. These observations are examined in the light of numerical simulations in the following paper.