Ten patients were operated on within one hour to 3 months after percutaneous mitral dilation. Operative analysis of the lesions demonstrated hemopericardium (n = 3), acute mitral insufficiency (n = 7), left atrial thrombus (n = 2), and atrial septal defect (n = 3). A conservative treatment of the mitral valve lesion was performed in 6 patients. All patients had uneventful postoperative courses. The complications presented in this series were either due to technical error or occurred in patients with relative contraindications to percutaneous mitral dilation (calcified commissures).