134 children with functional dyspepsia (FD) have been observed. It has been established that abdominal pain in children with functional dyspepsia was weak, developed before or after meal or physical exercise. The dysmotility-like dyspepsia predominated in infant (47.8 +/- 4.3%), the frequency of cases of ulcer-like dyspepsia prevails among older children 27.1 +/- 5.8%. Patients with FD had marked changes in their vegetative status. Hypersympathotonia and hyperparasympathotonia have been observed among these patients with hyperparasympathotonia prevailed in children with ulcer-like dyspepsia. The activity of sympatic part of vegetative system in patient with dysmotility-like dyspepsia was higher than that of parasympatic one. FD patients have been revealed to have vegetative dysfunction accompanied with high levels of serotonin (88.8 +/- 7.8 ng/ml, P < or = 0.05) and histamine (100.2 +/- 8.4 ng/ml, P < or = 0.05) in blood plasma. The highest level of blood histamine and the lowest level of blood serotonin have been determined in patients with ulcer-like dyspepsia, the increase of serotonine predominated in children with nonspecific dyspepsia. The determined changes could play role in the development of FD in childhood.