Attempts to improve nutrient utilization by the incorporation of proteolytic enzymes into dry diets for pigs have met with limited success (Dierick and Decuypere 1994) Liquid feeding provides an ideal environment for optimizing the action of feed additive enzymes, and an opportunity to pre-treat individual dietary components. Raw soya has a poor nutritive value and there is potential for improving the nutritional status by partial hydrolysis of native proteins that largely resist mammalian digestive tract enzymes. Such enzyme treatments may also improve protein availability in cooked soya. The objective of this experiment was to assess the effectiveness of pre-treating raw and autoclaved soya with a microbial protease on the growth performance of grower/finisher pigs.