In recent years, Medical science has been developed remarkably in treatment of malignant diseases. New treatment modalities, chemotherapy, radiotherapy and immunotherapy in patients with different types of neoplasm have cured some cases and increased their life long. On the other hand, considerable complications have also been developed for both patients and clinicians. Viral infections of oral cavity in patients receiving chemotherapy is ignored in most cases. Therefore, we aimed to evaluate viral infections in hospitalized patients receiving chemotherapy in Hematology department of Amiralam and Imam Khomeini Hospitals. On this account 84 patients with leukemia (AML,ALL, CML, CLL) and lymphoma ( hochkin and non hochkin) who were in immunosuppression phase after chemotherapy were evaluated in 3 months. Lower incidence of viral infections in comparison to the results of other countries were obtained.