Mononuclear leucocyte zinc was determined together with serum zinc, albumin and serum alkaline phosphatase activity before and after zinc supplementation (2 x 50 mg of zinc-gluconate daily during 3 months) in patients with alcoholic liver cirrhosis (n = 10), alcoholic chronic pancreatitis (n = 10) and Crohn's disease (n = 10). Initial mononuclear leucocyte zinc concentrations did not differ between the patient groups and the reference group (n = 10), whereas initial serum zinc values were lower in the patients with alcoholic liver cirrhosis and Crohn's disease. This difference disappeared, however, when serum zinc concentrations were corrected for albumin levels, which were lower in all the patient groups. Higher initial activity of serum alkaline phosphatase was found in the alcoholic patients. In all the patient groups serum zinc concentrations increased significantly after zinc supplementation. Only in patients with Crohn's disease was there also an increase in serum alkaline phosphatase and albumin. Mononuclear leucocyte zinc did not respond to zinc supplementation in any of the patient groups. The results of our study indicate that mononuclear leucocyte zinc is not a sensitive indicator of marginal zinc deficiency.