Purpose: Gaucher disease should be considered in the differential diagnosis of a patient with Epstein-Barr virus (EBV) infection who has unexplained or disproportionate splenomegaly.Patients and Methods: A previously asymptomatic adolescent with EBV-associated infectious mononucleosis and massive splenomegaly is described. He was found to have Gaucher disease on bone marrow biopsy, which was performed to exclude a hematologic malignancy. The diagnosis was confirmed by assay of β-glucosidase enzyme activity.Results: Regression of splenomegaly and improving hematologic indices.Conclusion: Patients with infectious mononucleosis and disproportionate organomegaly should be investigated to exclude a hematologic malignancy or an underlying storage disorder such as Gaucher disease.