We report a high incidence of subacute, chronic and sometimes occult intracranial subdural haematoma (SDH) occurring during intensive chemotherapy for acute myeloid leukaemia (AML) with a monoblastic component. Between March 1990 and January 1993, 86 AML patients from our institution were randomized in the multicentric French AML 90 trial. Eight patients (9%) presented a grade > 2 haemorrhagic event, which was intracranial SDH in five of them. All these five SDH patients had hyperleucocytic AML4 or AML5 and had experienced at least one lumbar puncture (LP) before SDH diagnosis (with intrathecal chemotherapy in four cases). SDH diagnosis was assessed on a brain computed tomography scan which was performed 1-9 d after initial SDH symptoms (mainly mild headaches considered a result of prior LP). All these five patients recovered from this severe event after a specified therapy. SDH does not appear to be an uncommon complication of AML4 and AML5 therapy. Its incidence might be under-reported because of poor symptomatology. Lumbar punctures, known to cause exceptional SDH in nonleukaemic patients, might trigger these haemorrhagic events, eventually in combination with other predisposing factors such a haemostasis disorders or leukaemic CNS infiltration.