Two cases with acute myeloblastic leukemia (AML M4-FAB) associated with diabetes insipidus (DI) are presented here. Both patients presented with hyperleucocytosis, One had a white blood cell count (WBC) of 150 x 10(9)/L and the second patient had 200 x 10(9)/L, One of these patients was a 40 year-old male and MRI of the hypophysis showed an infindibuler mass. This patient did not respond to remission induction chemotherapy and reinduction chemotherapy was given, The other patient was a 16-year-old male with a normal CT scan of the head. Both patients had DI with typical clinical and laboratory findings. The first patient died early on during reinduction chemotherapy and the second patient died of intracranial bleeding before induction chemotherapy was given, These findings are consistent with the data in the literature suggesting that the prognosis of AML associated with DI is poor and that these cases generally present with hyperleucocytosis.