1. The zinc contents of plasma, erythrocytes, polymorphonuclear leucocytes and mononuclear leucocytes from 18 normal control subjects, 31 patients with Crohn's disease and 15 patients with ulcerative colitis were measured.
2. Plasma zinc levels were low in Crohn's disease, particularly in malnourished patients, and related to plasma albumin concentrations, but were normal in ulcerative colitis.
3. Erythrocyte zinc levels were normal in both Crohn's disease and ulcerative colitis.
4. Mean polymorphonuclear leucocyte zinc levels were normal in Crohn‘s disease and ulcerative colitis. Ten per cent of Crohn's disease patients had subnormal levels, which were associated with inactive disease, while 10% had elevated levels, which were associated with active disease. Seven per cent of ulcerative colitis patients had subnormal levels. Mononuclear leucocyte zinc levels were normal in Crohn's disease and in ulcerative colitis.
5. Tissue zinc depletion occurs in only a few patients with Crohn's disease and ulcerative colitis.