The authors elaborated their own modification of the separation and labelling of autologous thrombocytes by means of 111indium-oxine which can be implemented in Czechoslovak departments of nuclear medicine with standard equipment. A total of 123 separations and labellings were made and 85 administrations to patients. The effectiveness of labelling by the described method was 79.5 +/- 6.9%, the separation yield of thrombocytes with regard to complete blood 44.3 +/- 13.8%. The aggregating capacity of the labelled platelets assessed in vitro after ADP stimulation (adenosine diphosphate) was 39.5 +/- 10.1% difference in optic density of platelet rich and platelet poor plasma which is evidence of the preserved viability of thrombocytes. "Recovery" during the 120th minute after administration of normal suspensions was 62.2 +/- 17.9%, the survival time of labelled thrombocytes 8.2 +/- 0.74 days. In patients with idiopathic thrombocytopenic purpura the "recovery" was 49.4 +/- 18%, the survival period 2.9 +/- 1.8 days. In patients after transplantation of the kidney complicated by acute rejection there was an increased accumulation of labelled platelets in the area of the kidney (count rate index 2.32 +/- 0.45). In normally functioning transplanted kidneys the count rate index was 1.42 +/- 0.06. On their own material the authors demonstrate other possibilities of clinical application of scintigraphy by means of labelled autologous platelets (a method hitherto not described in the Ccezhoslovak literature) for the detection of intracardial and arterial thrombosis.