A novel butadiene derivative of the formula: wherein Ring A is heterocycle, or benzene being optionally substituted by lower alkyl, alkoxy, nitro, hydroxy, substituted or unsubstituted amino or halogen, Ring B is heterocycle, or benzene being optionally substituted by lower alkoxy, lower alkylenedioxy or di-lower alkylamino, R1 and R2 are each H or lower alkyl, one of —COR32 and —COR42 is carboxyl, and the other is carboxyl being optionally esterified, or the corresponding amide or pyrrolidine derivatives, or a pharmaceutically acceptable salt thereof. Said compounds show excellent PAI-1 inhibitory activity and are useful in the prophylaxis or treatment of various thromboses such as myocardial infarction, intra-atrial thrombus in atrial fibrillation, cerebral infarction, angina pectoris, stroke, pulmonary infarction, deep venous thrombus (DVT), disseminated intravascular coagulation syndrome (DIC), diabetic complications, restenosis after percutaneous transluminal coronary angioplasty (PTCA), etc.