In massive pulmonary embolism where there may be evidence of right ventricular dysfunction and acute pulmonary hypertension, anticoagulation therapy alone may prove inadequate. In such situations use of thrombolytic agents produces an improvement in haemodynamics compared to anticoagulants alone, although studies to date have been too small to address the issue of mortality benefit. It would appear that all age groups gain benefit from the use of thrombolytics. Studies that have compared thrombolytic agents and anticoagulants are discussed. In addition, the issues of the choice of thrombolytic agent and the different modes of delivery of therapy are addressed.