Upper-extremity deep venous thrombosis and pulmonary embolism. A prospective study. We prospectively evaluated the prevalence of pulmonary embolism (PE) in 30 consecutive patients with proved deep venous thrombosis (DVT) of the upper extremity. Ten patients (seven male and three female; mean age, 43 years) had primary DVT, and 20 patients (14 male and six female; mean age, 52 years) had catheter-related DVT. Ventilation-perfusion lung scans were routinely performed at the time of hospital admission to all but one patient (one patient was critically ill, and he died four days after DVT diagnosis because of massive PE). Lung scan findings were normal in nine of ten patients with primary DVT, and they were indetermine in the remaining patient. By contrast, perfusion defects were considered highly suggestive of PE in four patients with catheter-related DVT; two patients had indeterminate lung scans, and 13 patients had normal scans. We conclude that PE is not a rare complication in upper extremity DVT, and that patients with catheter-related DVT seem to be at a higher risk. 