Correct and rapid diagnosis is pivotal to the practice of emergency medicine, yet the chaotic and ill-structured emergency department environment is fertile ground for the commission of diagnostic error. Errors may result from specific error-producing conditions (EPCs) or, more frequently, from an interaction between such conditions. These EPCs are often expedient and serve to shorten the decision making process in a high-pressure environment. Recognizing that they will inevitably exist, it is important for clinicians to understand and manage their dangers. The authors present a case of delayed diagnosis resulting from the interaction of a number of EPCs that produced a "perfect" situation to produce a missed or delayed diagnosis. They offer practical suggestions whereby clinicians may decrease their chances of becoming victims of these influences.