Colon absorption function was examined in twenty fife patients with active non-specific ulcerative colitis (15 persons with the distal form and 10 with left-side form investigate by rectal antipyrin test. The state of absorption was estimated on duration of antipyrin half-absorption, on attainment of its maximal concentration and on level of its salivary concentration. Most of patients (n = 19) with active non-specific ulcerative colitis had disorders of colon absorption. This was demonstrated by reduced antipyrin absorption and decreasing amount of absorbed material. But in 6 patients with expressed destructive-inflammatory processes the antipyrin absorption was intensified. In patients with ulcerative colitis the disorders of colon antipyrin absorption depend on activity of inflammatory processes.