Sepsis and septic shock, are complex disorders that are a major cause of mortality in the intensive care unit. In spite of major advances in our understanding of the pathophysiology of sepsis, accurate prediction of susceptibility to sepsis, multi-organ dysfunction, and death, even in the setting of a seemingly similar burden of infection, continues to challenge critical care clinicians. Evidence from family-based studies and recent gene-association studies suggest that a significant portion of the apparent variability in susceptibility is due to genetic factors. Common sequence variations in genes coding for innate immune effectors, inflammatory mediators, and modulators of coagulation have received particular attention. This review will summarize and integrate the results of studies testing for associations between sequence variations in genes from these functional classes and susceptibility to sepsis and related clinical outcomes. The important insights on sepsis pathophysiology provided by these studies will be discussed along with the relevance of these findings to the design of future diagnostic approaches and therapeutic trials.