Hydrocortisone reduces the number of inflammatory leukocytes within tissues, but thus far the site of action on the multistep adhesion cascade leading to leukocyte extravasation has not been identified. We have recently developed a noninvasive in vivo reflected-light confocal microscopy technique to study this at sites of inflammation in human patients. In the present study, we evaluated the effect of preoperative intravenous hydrocortisone treatment on leukocyte trafficking after conjunctival inflammation induced by cataract surgery in human subjects in vivo. The surgery generated leukocyte rolling along the endothelial lining of conjunctival vessels. While preoperative hydrocortisone did not reduce the number of rolling cells, it significantly raised the velocity of individual rolling leukocytes and concomitantly reduced leukocyte emigration into conjunctival tissue. Immunohistology of conjunctival biopsies excised from the individuals studied provided circumstantial evidence that endothelial P-selectin might play a role in the surgery-induced up-regulation of the leukocyte rolling. Furthermore, hydrocortisone reduced surgery-induced P-selectin induction, suggesting a role for this selectin in the regulation of local leukocyte traffic into sites of inflammation in human conjunctiva. Taken together, these results suggest that control of the rolling velocity might be an effective way to adjust leukocyte traffic in vivo in human subjects.