Leukocytes are the main cellular elements of inflammatory and immune reactions of the organism. Leukocyte alterations are the consequence of an imbalance between the formation of leukocytes in the bone marrow and its elimination by the mononuclear phagocytic system. Factors that can modify leukopoyesis are varied and can lead to an alteration in the number of leukocytes or tumoral alterations of white cells (leukemias, lymphomas and plasma cell tumors). There is also a wide range of clinical manifestations that can derive from them: from very slight symptoms to life-threatening conditions. In some cases oral manifestations will be the first signs and it will be the dentist’s responsibility to identify the underlying disorder and guide the diagnosis of the patient. It is important to be familiar with the special management required for these patients, in which the dental treatment can affect the course of the underlying disease. The objective of this article is to review the literature concerning the oral manifestations and the considerations that must factor in the dental treatment of patients with leukocyte alterations.