[en] Using ¹¹¹indium oxine and ¹¹¹indium oxine sulphate as platelet labels, maximal labelling efficiency can be achieved already after 3 minutes at an incubation temperature of 37⁰C. Mean labelling efficiency values of about 90% are reached at a platelet count of >10⁹ platelets/ml, but the labelling efficiency is satisfactory also at a rather low platelet count of about 10⁶ platelets/ml (71% on average). Platelet labelling with these tracers allows the calculation of platelet half-life in vivo, and gamma-camera imaging of platelet aggregates in thrombosis and renal transplant rejection as well. In the present study, the platelet half-life is significantly shortend in patients with coronary heart disease (n = 15), peripheral vascular disease (n = 13) and primary hyperlipoproteinaemia (n = 32) in comparison with 106 controls. No age dependence of platelet half-life was found in the different groups of patients whereas in the control group, a significant negative correlation between age and platelet half-life was observed. (Author)