Infectious mononucleosis is an acute, viral, illness associa ted with a high incidence of splenomegaly. Spontaneous sple nic rupture is a rare but life – threatening complication of infectious mononucleosis.The authors report the case of a 19 – year – old patient with an infectious mononucleosis causing a spontaneous splenic rupture. When rupture occurs the mortality has been significant. The spleen may be vul nerable for the histopathologic changes that occur as a result of this illness. Two thirds of patients with infectious mono nucleosis develop an enlarged spleen, but in only 0,5 % of all patients will it rupture. Abdominal pain and tachycar dia are unusual in uncomplicated infectious mononucleosis and should alert a doctor to the possibility of spontaneous splenic rupture. The diagnosis of splenic rupture may be confirmed in a variety of ways. In this patient ultrasound and Rutkow’s criteria may aid in establishing the diagno sis. In patients with infectious mononucleosis suspected of having rupture of the spleen, a rapid but thorough asses sment and prompt implementation of appropriate manage ment should minimize the associated morbidity and mor tality. On the basis of review of the medical literature and of our own experience, we advocate emergent splenectomy for spontaneous splenic rupture in patients with infectious mononucleosis.