One hundred gram oral glucose tolerance tests (OGTT) were given to 6 normal human subjects after an overnight fast. From each subject, 100 ml of blood was collected at 0, 2 and 5 hours after the glucose load. Mononuclear cells (Boyum 1968) and erythrocytes (Gambhir, Archer and Bradley 1978) were prepared by the Ficoll-Hypaque technique and insulin binding was measured (Wachslicht-Rodbard et al. 1979;Gambhir et al. 1978). Monocytes were identified by latex bead ingestion and non-specific esterase staining in mixed mononuclear leukocytes and the binding to monocytes was calculated based on the percent of monocytes in mononuclear leukocytes.