The properties of polymer latices, their measurement, and their influence on emulsion paint performance are considered. Solution properties include pH, viscosity, non-volatile content, stability, particle size (distribution) and surface tension. Increasing the molecular weight (MW) of the latex polymer, for instance, resulted in an increase in scrubbability and enamel holdout for medium or fine particle size latices. The critical effect of particle size on overall paint performanceand on levelling and freeze/thaw stability is illustrated. -- AATA