The establishment of regional trauma centers in the United States has resulted in a significant reduction in morbidity and mortality from traumatic injuries. It has also led to a decrease in the incidence of delayed diagnosis of injuries ("missed injuries"), which are not detected during the initial evaluation of these patients. The surgeon managing an acutely injured trauma patient in the initial "golden hour" is faced with leadership, organizational, diagnostic, and therapeutic challenges. The algorithmic approach to the care of the trauma patient has led to the development of protocols to eliminate or at least reduce the incidence of these undetected injuries. The majority of these missed injuries are difficult to reliably detect by conventional diagnostic modalities, are usually asymptomatic, or attention was erroneously diverted to other more overt injuries. We report a case of a patient who sustained a traumatic laceration of his left hemi-diaphragm, which was detected only after positive pressure mechanical ventilation was discontinued. A proposed system of classification of delayed diagnoses is also presented.