The function of polymorphonuclear neutrophils from blood (B-PMN) and from exudates (E-PMN) was studied in healthy volunteers. The E-PMNs were isolated from skin windows with chambers and the chemotactic, phagocytic and Nitro Blue Tetrazolium (NBT) reducing activity measured and compared to that of simultaneously obtained B-PMNs. The chemotactic and random migration of E-PMNs in Boyden chambers measured by the leading front and by the chemotactic index were reduced compared with B-PMNs (p less than 0.01). Serum independent phagocytosis of paraffin oil emulsions was significantly increased (p less than 0.01) by E-PMNs after 12, 24 and 48 hours and not correlated to the function of B-PMNs. Opsonization with autologous serum increased the phagocytosis by both E-PMNs and B-PMNs, but mainly the latter. The NBT reduction by E-PMNs was increased (p less than 0.01) and positively correlated to the NBT reduction by resting B-PMNs. In contrast, there was no difference in NBT reduction between phagocytosing E-PMNs and B-PMNs. Mobilization of PMNs to an inflammatory focus in healthy subjects induces marked changes in the function, and B-PMN function cannot always be assumed to reflect the function of PMNs from inflammatory sites.