The influence of polyvinylpyrrolidone (PVP), a commonly used binder and adhesive, on the aggregation of spheroids coated with hydroxypropylmethylcellulose (HPMC) was studied. The aggregation propensities of spheroids coated by HPMC alone and by HPMC with polyethylene glycol (PEG) were compared with those coated by HPMC with PVP and the viscosity of the coating solutions determined. The coating was conducted at a maximum spray rate of 11 g/min to avoid premature termination of the coating process at higher spray rates due to uncontrollable aggregation of spheroids. PVP was able to reduce the extent of aggregation of spheroids. It was more effective in reducing spheroid aggregation than PEG. The reduction in spheroid aggregation propensity was ascribed to viscosity lowering effects of PVP. The viscosity of the coating solutions determined over the temperature range of 28-58 degrees C was found to increase in the following order: HPMC-PVP<HPMC-PEG<HPMC.