It is well known that non-specific mucosal alterations can occur during diseases of the leukopoetic system. In most cases they are an early sign and therefore provide the opportunity for timely diagnosis of the disease. In this clinical study type and frequency of oral lesions, gingival and periodontal indices, and hematologic status were examined at the time of diagnosis of the different types of acute leukemia. The results showed a significant difference in the frequency of oral lesions between acute myelogenous and acute lymphoblastic forms, irrespective of age and sex of the patient. There was no correlation between type and frequency of lesions and hematologic status.