Quantitative in vivo migration of leukocytes into tissue has been analyzed by a new technique. This new method differs from previous methods by utilizing tape stripping of skin rather than skin abrasion, thereby preserving dermal vascular endothelium and the basal lamina of the epidermis. By preserving these two physiologic membranes, this technique simulates physiologic leukotaxis. Results in sixteen control patients revealed a mean of 1.12 X 10(6) leukocytes per chamber per 24 hours. In four patients with immunodeficiency this value was of 9.26 X 10(3) leukocytes per chamber per 24 hours clearly distinguishing this group from control groups (p less than 0.01). Reproducibility of duplicate chambers, simplicity, and comfort of the plastic chambers enhance its use by the clinical investigator as a secreening test for abnormalities in leukocyte movement.