The aim of this clinical prospective study was to determine the effect of indobufen upon synthetic graft patency in femoral-popliteal/crural position. 15 operated patients were observed during the three-month period. One day prior to operation patients were given 400 mg of indobufen perorally. The same daily dose was continued on the first postoperative day as well as during the following three months. Blood levels of 6-keto-prostaglandin (PG) F1alpha (stable metabolite of PGI2) and thromboxane (Tx) B2 (stable metabolite of TxA2) were determined by RIA before indobufen administration, i.e., one day and three months postoperatively. The three-month patency of grafts was achieved in 86% of cases. Plasma levels in all observed time periods showed significantly reduced TxB2, increased 6-keto-PGF1alpha, and higher PGI2 levels compared with TxA2 that could suggest the normalization of aggregation/antiaggregation process.