We describe three patients with chronic granulocytic leukaemia who developed impaired visual acuity in association with high leucocyte counts. Two of the patients were in the chronic phase of their disease and the third developed visual symptoms at the time of blastic transformation. Fundoscopy showed retinal haemorrhages and exudates and a vascular picture consistent with hyperviscosity. We propose the term 'hyperleucocytic retinopathy' for these appearances. Two of the patients derived rapid benefit following leucapheresis and the visual acuity of the third patient improved following treatment with cytotoxic drugs.