AbstractValues of the unperturbed dimensions of poly(2‐hydroxyethyl methacrylate) have been determined in five non‐ideal solvents using viscometric data and a number of different theoretical treatments. Values of the steric factor σ, the characteristic ratio C∞ and the expansion factor α were also calculated. There was some variation of all these parameters with solvent but on the whole they were comparable to values for polymethacrylates with non‐polar side groups of a similar size.