Concentration of fecal pancreatic elastase 1 has been claimed to be a highly sensitive and specific noninvasive test for exocrine pancreatic function. The aim of our study was to investigate variations in elastase concentration within one stool passage and from day to day. For the analysis of the variation of fecal elastase within one stool passage, we utilized 3 different samples collected from 8 patients. Further, we assessed the individual day to day variation of fecal elastase using stools collected on 3 consecutive days from 40 patients. For the determination of pancreatic elastase 1 in stool we used an ELISA kit. We found a relatively considerable variation of fecal elastase concentration within one stool passage (n = 8, mean CV = 22%, range 4.6-83.1%) and from day to day (n = 40; mean CV = 26%, range 2.4-61.1%). Therefore, we recommend routine analysis of more than 1 stool sample collected on different days for fecal elastase and to use a borderline area of +/- 25% of the recommended cut off of 200 micrograms/g stool for the diagnosis of pancreatic insufficiency.