Size distribution information was used to monitor time-dependent agglomeration in aqueous solutions of a high molecular mass polyacrylamide. Although the individual polymer molecules had diameters in the order of 0.4 mu m, a high number of agglomerates were seen that may contain four to six polymer chains. As the solution age increased, a significant level of larger microgels (2-15 mu M) were also detected. The addition of salts or organic cosolvents modified the solvation properties, altering the extent and rate of agglomeration. The presence of 2%-v/v formamide had a significant effect, substantially reducing agglomeration and increasing solution stability.