Clinical and haematological remissions at the stage of acute transformation of chronic granulocytic leukaemia are uncommon. This communication records a case in which these remissions were accompanied by the rare additional evidence of a cytogenetic remission. CASE REPORTThe patient was a 65-year-old housewife when chronic granulocytic leukaemia was diagnosed in July 1964. During the following three and a half years she attended the outpatient clinic regularly, and was treated with intermittent courses of busulphan 4 mg. daily as determined by the increase in the white cell count.Her first admission to hospital was on 31 January 1968, when she gave a history of rapid deterioration in general health over the preceding two weeks with severe malaise, night sweats, and anorexia. The spleen was palpable 11 cm. below the left costal margin.