Finding a simple reproducible routine test is relevant for the determination of post-pyloric feeding tolerance.Aim. To evaluate in a pilot study the usefulness of acetaminophen absorption test with post-pyloric drug administration in patients with generalized secondary peritonitis.Materials and methods. Acetaminophen absorption test was performed in patients with generalized secondary peritonitis. 0.5 g of drug was administered into the lumen of the small intestine through the nasojejunal tube and after 5, 10, 15, 20, 30, 40, 50 and 90 min its blood level was determined. The first group (n=14) of variables was taken from patients whose test was performed immediately after the surgery. The second group results (n=10) were obtained from the same patients who were tested when they were able to absorb >1 l/day of enteral nutrition without signs of intolerance.Results. When comparing the concentration of acetaminophen in the blood after the drug administration into the bowel of patients with peritonitis immediately after surgery and at the time when the assimilation of bowel feeding had become possible, it was found that the most significant differences were detected within the time interval of 5–20 minutes after the drug administration (P<0.001). This time interval is optimal for harvesting blood samples during the acetaminophen test procedure.Conclusion. Bowel absorption of acetaminophen may be informative for predicting the feasibility of adequate post-pyloric enteral feeding of patients with generalized secondary peritonitis.