Acute leukaemia is the most common form of childhood cancer. The aim of this paper was to underline the importance of oral manifestations in children with acute leukaemia. The disease and its treatment can directly or indirectly affect oral health. Oral manifestations are gingival inflammation and enlargement. Leukaemic cells are capable of infiltrating the gingiva and the deeper periodontal tissues which leads to ulceration and infection of oral tissues. Gingival bleeding is a common sign in patients with leukaemia. Symptoms include local lymphadenopathy, mucous membrane Petechiae and ecchymoses. Cytotoxic drugs have direct effects like mucositis, involving atrophy, desquamation and ulceration of the mucosa, with increasing the risk for local and systemic infections. Leukaemia can directly influence dental care and dental treatment, while oral lesions may have life-threatening consequences. Knowledge and skills among dentists may also not be adequate to treat children with acute leukaemia. It is therefore imperative that all stomatologists be aware of dental problems that occur in leukaemia in order to be able to effectively carry out appropriate measures to mitigate these problems.