In 9 children out of 36 with ALL examined post mortem at the Department of Pathology of the Medical University of Pécs in the period 1960--1978 leukaemic infiltrates were not found at all ("total remission"). 7 cases out of the 9 observed during the last 5 years. The remaining 27 cases could be divided into two groups: at 20 children nuclei of the leukaemic cells have shown marked gyrification. Survival of children of this group was 10.8 months. At the remaining 7 children the surface of the cell nuclei appeared to be smooth. The survival in this group was 3.6 months. These data support the hypothesis according to which ALL of the children and T cell malignant lymphomas may be of two types. Those with gyrificated and with non-gyrificated nuclei. The considerable difference in survival of patients with these two types of leukaemia suggests that the morphology of the cell nuclei i.e. "gyrification" or "non-gyrification" of them may be used in estimation of the prognosis.