Misdiagnosis of the Zollinger-Ellison syndrome due to hyperlipidemia. Most authorities feel that diagnosis of the Zollinger-Ellison syndrome is established when the serum gastrin level is greater than 1000 pg/mL (1000 ng/L) in a patient with gastric acid hypersecretion and clinical manifestations consistent with the diagnosis. A patient with recurrent peptic ulcer disease is reported who was thought to have had the Zollinger-Ellison syndrome based on two serum gastrin level measurements greater than 1000 pg/mL (1000 ng/L). Subsequent evaluation revealed the gastrin elevation to be spurious because the sample was hyperlipidemic. Lipemic serum samples may yield falsely elevated serum gastrin determinations as determined by radioimmunoassay. 