Intestinal digestibility of food protein is one of the important factors of most protein evaluation systems. Therefore it was determined in the experiments with duodenal infusions of foods (Hvelplund, 1985) or using mobile bags (Sauer et al., 1983; Hvelplund, 1985; de Boer et al., 1987; Antoniewicz et al., 1992). To avoid the use of cannulated animals, in vitro enzymatic methods have been developed (Antoniewicz et al., 1992). Incubation of food with pepsin and pancreatin correlates with the digestibility of food protein (Akeson and Stahmann, 1964) and is suitable (r = 0·95 to 0·99) to determine protein digestibility in pig foods (Babinszky et al., 1990). The aim of the study was to develop the best conditions of pepsin-pancreatin digestion and to evaluate the predictive ability of the method to determine protein disappearance measured using mobile bag technique.