The fractal dimensions of aggregates of latex particles coated by poly(ethylene oxide) (PEG) have been measured in worse-than-theta-solvents for different electrolyte concentrations and temperatures. For the lowest molecular weight PEO studied (2 x 10(4)), the measured fractal dimension of 2.1 was almost independent of temperature over the range studied. The value corresponds to partially reversible cluster aggregation, which leads to relatively compact aggregates. For the highest molecular weight PEO studied (6 x 10(5)), the fractal dimension decreased significantly (from 2.4 to 1.7) with temperature, signifying the generation of more ramified aggregates. The results obtained for this hydrophilic polymer contrast markedly with those previously published for the aggregation of latexes coated by the hydrophobic polymer poly(N-isopropylacrylamide), which becomes hydrophobic as a result of a coil-to-globule transition.