Serum zinc concentrations are decreased in patients with a variety of clinical disorders including cirrhosis, nephrotic syndrome and renal insufficiency. Urinary zinc excretions are increased in the first two disease states. Symptoms of acute zinc deficiency (anorexia, dysfunction of smell and taste and mental and cerebellar disturbances) and chronic zinc deficiency (growth retardation, anemia, testicular atrophy and impaired wound healing) are common in these patients. It remains unresolved whether these low serum zinc concentrations in these disease states are indicative of true symptomatic or asymptomatic zinc deficiency, or merely reflect a decrease in available zinc-binding proteins, as well over 90% of serum zinc is bound to protein in normal subjects. The correlation between serum zinc and albumin concentrations, reportedly the major zinc-binding protein, is unimpressive. Studies of serum and urine binding of added radiozinc65using Sephadex G-200 gel column chromatography and polyacrylamide gel electrophoresis suggest most of the radiozinc is bound to a protein with a molecular weight near albumin (68,000). Polyacrylamide gel electrophoresis suggests this might be a prealbumin. The low serum zinc concentration in the patient with nephrotic syndrome does not appear to be due to loss of zinc bound to urinary protein.