Massive PE is a devastating clinical entity often undiscovered until autopsy. Acute right ventricular failure may progress to death within minutes to hours after the embolic event and prompt diagnostic and therapeutic intervention are imperative. The diagnosis heavily relies on clinical suspicion together with ventilation-perfusion scanning. Echocardiography may have a role in select patients to aid in the recognition of PE with right ventricular failure and to guide therapy. Clinical instability may hinder the diagnostic evaluation and delay therapeutic intervention. Oxygen is administered and, when necessary, intubation and mechanical ventilation are undertaken. In the setting of hypotension supportive therapy includes vasoactive medications, such as norepinephrine. Intravenous fluids should be administered cautiously. Therapeutic options aimed directly at reducing the embolic burden include systemic thrombolytic therapy, surgical embolectomy, and the use of intrapulmonary arterial catheter techniques. In the absence of contraindications, thrombolytic therapy should be strongly considered in hypotensive patients. Surgical embolectomy for acute PE is controversial, but this modality appears to have a role in select patients. Various intrapulmonary arterial catheter techniques, with or without low-dose thrombolytic therapy, have been used successfully to reduce the embolic burden, although no particular technique appears to have clear advantages over others. Placement of an inferior vena caval filter may prevent additional, potentially fatal emboli and appears appropriate in select patients with massive emboli.