The aqueous solution of a thermoresponsive polymer, poly[2-(2-ethoxy) ethoxyethyl vinyl ether] poly(EOEOVE), contains a tiny amount of large polymer aggregates at low polymer concentrations far below the lower critical solution temperature (similar to 40 degrees C). The molar mass M-w,M-slow, radius of gyration < S-2 >(1/2)(slow) and hydrodynamic radius R-H,R-slow of the aggregating component of poly(EOEOVE) were obtained by simultaneous static and dynamic light scattering as functions of the polymer concentration and temperature, while the weight fraction w(slow) of the component was estimated by size-exclusion chromatography. The M-w,M-slow dependencies of < S-2 >(1/2)(slow) and R-H,R-slow as well as the ratio < S-2 >(1/2)(slow)/R-H,R-slow indicated that the poly(EOEOVE) aggregate takes a sparsely branched polymer-like conformation. We have analyzed the structure of the aggregate, using the branched polymer model of random type. The M-w,M-slow dependence of < S-2 >(1/2)(slow) obtained was favorably compared with this model with reasonable structural parameters. (c) 2006 Wiley Periodicals, Inc.