Bowel sounds have a close correlation to the bowel peristalsis. By analysing these sounds--using Heinkelmann's method--sounds can be expressed by objective and calculable figures. We compared the effect of ceruletide, a hormone, with the cholinesterase inhibitor neostigmine and the alpha-adrenergic blocking substance dihydroergotamine. One of the drugs was injected twice daily in patients following operations in the gastrointestinal tract starting on the 3rd and 4th p.o. day. A group of 10 patients received ceruletide in a dose of 0,3 micrograms/kg body weight and of 0,5 micrograms/kg body weight, another 10 neostigmine (0,5 mg per single dose) and 10 patients dihydroergotamine in a dose of 1 mg. Ceruletide proved to be superior to the other drugs in both groups. Its advantage is exciting an ordered propulsive peristalsis. In cases of prolonged postoperative bowel atony or paralysis ceruletide is a helpful drug. Severe side effects were not seen.