The often fatal sepsis syndrome is characterized by the systemic release of inflammatory mediators, which is regulated and counterbalanced by the coordinated expression of anti-inflammatory molecules. The magnitude of sepsis-induced tissue injury and subsequent risk of infectious complications is dictated by the balance between the expression of pro- and anti-inflammatory mediators. As our understanding of the pathophysiology of sepsis continues to evolve, we have gained a greater appreciation for the profound effects that sepsis and similar states of overwhelming stress have on host innate and adaptive immunity. Impaired leukocyte function in sepsis has important clinical consequences, as high mortality rates have been observed in patients who display evidence of sepsis-induced immune dysregulation. Functional defects in leukocytes isolated from patients with sepsis include diminished expression of important cell surface molecules, dysregulated cytokine production, alterations in antigen-presenting ability, and accelerated apoptosis. In this article, we review the current literature supporting the notion that dysregulation of host immunity occurs during sepsis syndrome, and describe novel therapeutic interventions directed at augmenting host immunity during sepsis.