Pulmonary embolism (PE) is a common clinical entity, although the signs and symptoms that accompany it are nonspecific. This has led to the development of several diagnostic algorithms for diagnosis of PE. These approaches combine noninvasive tests such as ventilation/perfusion (V/Q) lung scanning, impedance plethysmography, and ultrasound, with invasive techniques such as venography and pulmonary angiography. To investigate the manner in which clinicians select and use these various diagnostic strategies, we retrospectively reviewed 316 consecutive cases of suspected PE to determine the sequence and type of diagnostic strategy employed by clinicians. We found that in the majority of cases, physicians chose not to further pursue a diagnosis of PE if the V/Q scan was nondiagnostic. These results suggest that physician behavior is often at variance with published clinical recommendations and that the implementation of clinical practice guidelines needs to be further examined.