In this article, the influences of five operating variables on the molecular weight (or K-value), polydispersity index (PDI), as well as polymerization yield of emulsion poly (vinyl chloride) in batch reactor were investigated simultaneously using Taguchi experimental design approach. The variables were temperature (T), water to monomer weight ratio (r), concentrations of initiator ([I]) and emulsifier ([E]), and agitation speed (S). Statistical analysis of results revealed the significance order of factors affecting the product qualities and quantity. It was found that the reaction temperature is the principal operating factor to control the molecular weight, and this is attributed to promotion of chain transfer reactions to monomer in this system. The effect of this factor on PDI is also comprehensively discussed. The significance sequences of important factors on yield are: S > [E] > r. The polymerization yield increases with S and [E] but decreases as r is increased. The relative optimum condition for a typical paste application was also determined using overall evaluation criteria. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2739-2746, 2009