The normal range for adult blood dendritic cells (DC) has not been established. Blood DC counts were assayed directly from blood for 16 female and 11 male healthy adults with an age range of 22-60 years old (median, 46 years). DC were defined as lineage 1-negative/dim, CD34-negative/dim, and HLA-DR-positive within the total peripheral blood leukocyte (PBL) population. Impedance counter complete blood counts were used with flow cytometry percentages to calculate the absolute DC count and DC percentage of mononuclear cells (MNC). The normal adult ranges for DC calculated as the mean +/- 2SD were 0.16-0.68% PBL, 0.55-1.63% MNC, and 13-37 DC/microL of blood.