Many cases of immuno-allergic thrombocytopenia complicated by serious thromboembolism induced by heparin or other heparinoids such as pentosan polysulphate have been reported. This case is of interest for two reasons: first of all, it was induced by pentosan polysulphate and then reactivated by secondary administration of heparin; secondly, it was complicated successively by an infero-apical myocardial infarction with probable spontaneous lysis of a coronary thrombosis because coronary arteriography performed one month later was normal, and then by massive biventricular thrombosis requiring surgical thrombectomy under cardiopulmonary bypass. Tests of platelet aggregation were positive to standard heparin and to several low molecular weight fractions. The outcome was favorable when the responsible substances were withdrawn.