At present there is no simple, reliable and non-invasive method for monitoring progression and improvement in diabetic microangiopathy. However, some diabetic patients with severe microvascular complications show a fairly specific pattern of impaired left ventricular function (abnormal relaxation, cavity filling and wall thinning) and abnormalities of haemorheology (increased viscosity, erythrocyte rigidity and beta-thromboglobulin and decreased threshold for platelet ADP aggregation). A single-blind, 6-months' crossover study of an antiplatelet agent, ticlopidine, was conducted in 20 diabetics with clinical evidence of microvascular disease. Response to therapy was monitored by digitised M-mode echocardiographic analysis of left ventricular diastolic function and haemorheology. All patients had abnormal basal values with no significant change during the 3-month placebo run-in period but, although significant alterations in viscosity, erythrocyte deformability, beta-thromboglobulins and ADP threshold were observed, no change in left ventricular function was detected. It is concluded that, while it may be possible to alter abnormal haemorheology in diabetes, there was no change in one parameter of microvascular end-organ damage.