Yeast suspensions which are negatively charged have been flocculated using a cationic polyelectrolyte. The initial rate of flocculation and growth of the floc particles were dependent on the flocculant dosage. The average particle size increased with increasing flocculant dosage. The maximum average particle size occurred at the optimum flocculant dosage. For flocculant dosages greater than the optimum dosage, the average particle size decreased. The optimum flocculation conditions for this cationic flocculant were related to a reduction in the magnitude of the zeta potential. The cationic polymer chains can adsorb via electrostatic interactions such as unlike charge attraction and hydrogen bonding onto the yeast particle surface. The flocculant can also form bridges between yeast particles. Micrographs of the flocculation process indicate an increasing particle size with time. The results obtained here indicate that flocculants may be screened by measuring the average particle size and the zeta potential of the suspension.