In order to correct the system pressures predicted for butadiene + styrene by the model proposed by Wilhelm and Collier (1948), a different approach has been adopted to evaluate the liquid activity coefficients for butadiene and styrene using their reported pressure measurement for butadiene + styrene at 0 degrees C, and a simple temperature function has been used for extrapolating these liquid activity coefficients to higher temperatures. The validity of the proposed approach is verified by some of the hitherto proprietary experimental results.