The process of surgical decision making is based on both general principles that are amenable to evaluation using rigorous techniques of clinical research and the intangible element of surgical judgment that seeks to apply those principles to the care of an individual patient. The role of surgical judgment is inescapable, even though it is intrinsically subjective and recalcitrant to objective evaluation, for a host of factors modify the application of principle in each patient, and render the circumstances of a given problem sufficiently distinctive, that evidence must be tempered with common sense. We have tried to provide, through an evidence-based approach to a series of questions, the rationale for the basic principles that should guide the clinician in initiating or modifying source control, recognizing that sound clinical judgement demands, at times, that these be set aside. In the individual patient, evidence of clinical improvement is the most important marker of the approach selected. Evaluation of the adequacy of source control in the critically ill patient can be difficult. As with other modes of anti-infective therapy, effective source control measures are expected to result in clinical improvement, reflected in: Resolution of clinical signs of sepsis or systemic inflammation. Bacteriological resolution. Evidence of reversal of the metabolic sequelae of infection, with normal progression of wound healing, reflected in the formation of granulation tissue, and epithelialization. Radiographic evidence of control of an infectious focus. Prevention of further organ dysfunction, and resolution of existing organ dysfunction. Survival. Evaluation of the adequacy of source control may necessitate planned reoperation. The adequacy of débridement of necrotizing soft-tissue infections can be assessed by repeat exploration under general anesthesia, continuing the process until there is evidence of healthy granulation tissue throughout the wound. Planned reexploration is also indicated for patients with diffuse intestinal ischemia to ensure bowel viability. The appropriate interventions to determine the adequacy of source control are dictated by the clinical circumstances. A residual or recurrent abscess can usually be demonstrated by CT or ultrasound examination, while resolution of an abscess cavity can be monitored using sinograms. The diagnosis of persistent or evolving tissue necrosis is guided by the clinical setting. Retroperitoneal necrosis can be detected by CT, while sigmoid ischemia following aortic aneurysmectomy can be evaluated by sigmoidoscopy. Occasionally diagnostic peritoneal lavage assists in establishing a diagnosis of gut ischemia; the lavage fluid appears bloody with established ischemia. The diagnosis of an infected foreign body requires an appropriate history and is supported by recurrent bacteremia or by positive cultures drawn retrograde through an indwelling vascular or peritoneal dialysis catheter. Finally, ongoing contamination from a breach of the gastrointestinal tract can be documented by appropriate contrast studies. The general principles that guide the use of source control techniques in the management of the patient with severe sepsis or septic shock are readily articulated. Their implementation in practice, however, is more complex, and does not, as a rule, lend itself to simple algorithms that are applicable in all cases. Moreover evidence-based support for these principles is weak. In the final analysis, the elusive process of experienced surgical judgement is invaluable for all but the most straightforward problems.