Mounting evidence suggests that beside well established factors, such as virulence of pathogens or site of infection, individual differences in disease manifestation are a result of the genetic predisposition of the patient on an Intensive Care Unit (ICU). Specific genetic factors might not only predict the risk to acquire severe infections but also to develop organ dysfunction or ultimately to die. Thus, the advent of molecular techniques allowing screening for a wide variety of genetic factors, such as single nucleotide polymorphisms in genes controlling expression of important mediator systems in patients as well as their purposeful targeting in animal models of sepsis, are revolutionizing understanding of pathophysiology in the critically ill. Molecular tools are about to challenge ''state-of-the-art'' diagnostic tests such as blood culture as they not only increase sensitivity but dramatically reduce time requirements to identify pathogens and their resistance patterns. Similarly, knowledge of genetic factors might in the near future help to identify ''patients at risk'', i.e. those with a high likelihood to develop organ dysfunction or to guide therapeutic interventions in particular regarding resource-consuming and/or expensive therapies (''theragnostics''). While therapeutic options in molecular intensive care medicine, such as stem cells in the treatment of organ failure or therapeutic gene transfer are possible along the road and might become an option in the future, recombinant DNA technology has already a well defined role in the production of recombinant human proteins from insulin to activated protein C.