Over two decades an abundance of knowledge has been accumulated focus­ ing on the understanding of the molecular and cellular pathomechanisms of stressful conditions like systemic inflammation and sepsis. We have learned that there is a clear correlation between the magnitude of the inciting traumatic event and the degree of inflammatory dysbalance. The immunoinflammatory disintegration comprises a simultaneous col­ lapse of the otherwise very smoothly balanced pro- and antiinflammatory vectors of cytokine regulation. Most recently, we understood that it is predominantly the dysregulation of antiinflammatory mediators that plays a pivotal role for the phenomenon of trauma-induced depression or paralysis of cell-mediated immune responses. The substantial intellectual and logistic investments of numerous investi­ gators towards understanding the biology of sepsis inevitably lead us towards a rewarding status in terms of reaching spheres of clinical relevance. From the evolutionary collection of a multitude of ex-vivo and in-vivo immuno­ mechanistic parameters, some were found to represent most significant bio­ logical markers to support the clinician to characterize better the severity of inflammatory illness and to predict outcome. Chapter one of this book, authored by G. Grass and E.A.M. Neugebauer, analyses elegantly our current knowledge on the assessment of the immuno­ logical status in terms of risk and prognosis of sepsis.