The proportions and absolute numbers of helper and suppressor T-cells in 40 patients with inflammatory bowel disease and 22 control subjects were determined, using the monoclonal antibodies OKT 4 and OKT 8. There were no significant differences in helper or suppressor cell proportions among 15 steroid treated patients with active inflammatory bowel disease, 10 patients with inactive inflammatory bowel disease, 10 patients with other gastrointestinal diseases, or 12 normal control subjects. In contrast, 15 patients with active inflammatory bowel disease not treated with corticosteroids manifested increased proportions of helper cells and decreased proportions of suppressor cells (p less than 0.001), compared with all other patient groups and to normal controls. When absolute numbers of helper and suppressor subsets were measured, these alterations in proportions of helper and suppressor cells were primarily attributable to decreased counts of suppressor T-cells both in patients with active Crohn's disease and in those with ulcerative colitis (p less than 0.01). In four patients undergoing serial study, the helper/suppressor ratios appeared to rise and fall respectively with clinical exacerbations and remissions of disease. These data provide additional evidence for the involvement of cellular immune systems in these disease processes.