Staliński J. 1994. Digestion, defecation and food passage rate in the insectivorous bat Myotis myotis. Acta theriol. 39: 1-11.The coefficient of dry mass digestibility (DMD) in the insectivorous bat Myotis myotis (Borkhausen, 1797), fed American cockroaches, is 69.3%. This is comparable with the average digestibility and assimilation coefficients in insectivorous mammals and birds, but it is much lower than estimated in previous studies on Insectivorous bats. The rate of passage of food marked with basic fuchsin (ts = 25, tso = 44, t9o = 77 minutes) and the defecation rate indicate extremely rapid digestion of food, which is connected with the feeding and foraging strategies of insectivorous bats. It is concluded, that previous estimations of bats' food consumption under natural conditions were lowered by the assumption of high digestibility of food or insignificant amount of feces defecated outside the rest place.