Measurement of tryptic and chymotryptic activity in the faeces was not disturbed by bacterial proteolytic activity of different bacteria such as proteus, pseudomonas, coli, enterococci, bacteroides. Both activities within a group follow a logarithmic normal distribution. Lower limit of the standard deviation is 51% upper limit 129% for tryptic activity, respectively 60 and 170% for chymotryptic activity. There were no differences in chymotryptic activity between the 10 age groups comprising 157 healthy children, whereas a significant difference could be found for tryptic activity between premature and older children. Daily fluctuations of the enzyme activities are quite high in the same individual, and only reduced in "bottlefed" infants with constant nutrition. In prematures and very young infants chymotryptic activity predominates, later tryptic activity. Influence of increased and decreased bowel movements on deviation of the data was tested. There was, however, no real alteration of enzyme activity due to the bowel dysfunction beyond the standard deviation of the control groups. But passage time and nutrition have to be considered beside other factors in the wide distribution of the enzyme activities and the latter limits the value of this method.