Acute pulmonary embolism (PE) ranges from asymptomatic to often fatal, incidentally discovered emboli to massive embolism causing immediate death. Acute PE may occur rapidly and unpredictably and may be difficult to diagnose. Mortality and complications can be reduced by prompt diagnosis and therapy. Untreated PE is associated with a mortality rate of approximately 30 percents. Most patients with PE have endogenous fibrinolysis, although it is not effective enough to prevent PE. A case of spontaneous remission of untreated acute PE has not previously been reported. Here we present a case of spontaneously resolved acute PE without any treatment.