Gelatinous degeneration of marrow is a rare histological disorder associated with chronic debilitating diseases, such as anorexia nervosa, AIDS and postchemotherapy aplasia. Solid tumours have been associated with this condition but it has been reported in only two patients with leukaemia. In these cases leukaemia and gelatinous degeneration were diagnosed simultaneously. In the case reported here, a 48 year old man, gelatinous degeneration was the only histological finding observed more than two years before the diagnosis of acute myelogenous leukaemia with monosomy 7. The significance of hyaluronic acid deposition remains uncertain. Two hypotheses have been put forward: (1) that gelatinous degeneration occurs during tissue repair; and (2) that gelatinous degeneration inhibits haemopoiesis by altering the microenvironment of the bone marrow. In the case reported here, the presence of monosomy 7 suggests that myelodysplasia was the underlying disorder which finally evolved into acute leukaemia.