Sixteen cases of mononucleosis due to cytomegalovirus, are presented. The selection of patients was based on clinical criteria. Symptoms are compared with another series of patients affected with mononucleosis by Epstein-Barr virus. We have not found differences comparing the fever, cervical adenopathies and faringoamigdalitis. Differences were significant in hepatomegaly. We conclude that the clinical picture of cytomegalovirus mononucleosis is very similar to those of the Epstein-Barr mononucleosis.