Sepsis is associated with failure of multiple organs, including failure of the immune system. The resulting 'sepsis-associated immunosuppression' resembles a state of immunological anergy that is characterized by repeated 'infectious hits', prolonged multiple-organ failure, and death. As a consequence, adjunctive treatment approaches using measures of immunostimulation with colony-stimulating factors (CSFs) were tested in animal experiments and clinical trials. Herein, data from randomized clinical trials will be discussed in the context of a recently published meta-analysis investigating the effects of granulocyte- and granulocyte-macrophage colony-stimulating factor therapy in patients with severe sepsis and septic shock.