We report viscometric data collected in a Couette rheometry on dilute, single-solvent polystyrene (PS)/dioctyl phthalate (DOP) solutions over a variety of polymer molecular weights (5.5 x 10(5) < M-w < 3.0 x 10(6) Da) and system temperatures (288 K < T < 318 K). In view of the essential viscometric features, the current data may be classified into three categories: The first concerns all the investigated solutions at low shear rates, where the solution properties are found to agree excellently with the Zimm model predictions. The second includes all sample solutions, except for high-molecular-weight PS samples (M-w >= 2.0 x 10(6) Da), where excellent time-temperature superposition is observed for the steady-state polymer viscosity at constant polymer molecular weights. No similar superposition applies at a constant temperature but varied polymer molecular weights, however. The third appears to be characteristic of dilute high-molecular-weight polymer solutions, for which the effects of temperature on the viscosity curve are further complicated at high shear rates. The implications concerning the relative importance of hydrodynamic interactions, segmental interactions, and chain extensibility with increasing polymer molecular weight, system temperature, and shear rate are discussed. (c) 2006 Wiley Periodicals, Inc.