The indices of serotonin metabolism in cerebrospinal fluid (CSF) and blood were studied in 43 patients with nontraumatic intracerebral hemorrhage in the interval from 1 - 2 to 28 days after the onset of the disease. The considerable increase of tryptophan, serotonin and its main metabolite 5-hydroxyindoleacetic acid (5-HAA) in CSF and blood was found. The relationship between liquor and blood serum serotonin levels, hemorrhage focus size, severity and outcome of disease was also observed. There were no significant differences between serotonin, 5-HAA, free and bound serotonin levels in patients with the break of blood into different part of liquor space. The possible mechanisms of alteration of serotonin metabolism in patients with intracerebral hemorrhage were discussed.