An important emerging paradigm in the understanding of renal disease is the recognition of the central role of inflammation in the initiation and progression of acute and chronic kidney injury. These advances have led to an increasing awareness of the importance of leukocytes (white blood cells (WBC)) in the pathogenesis of renal disease, and the necessity for a greater understanding of the specific roles of different WBC lineages. All aspects of WBC function have been implicated in aspects of renal disease. In many cases soluble factors derived from these cells (cytokines, complement, immunoglobulins, etc.) having effects remote from the secreting cells are involved, while in other cases there is apparently more direct involvement of infiltrating cells themselves acting on their immediate surroundings. This highlights the importance of understanding the dynamic behavior of specific WBC cell types and their interactions with the intrinsic cells of the kidney during injury. New insight into this question is promised by recent developments in imaging technology that allow WBC movement and interactions with endothelial or epithelial cells or with the extracellular matrix to be visualized within tissues, even in the relatively unperturbed setting of intact organs in the live animal.