Since Inoue et al introduced a specially designed balloon catheter for percutaneous mitral valvuloplasty (PMV) in 1984, the Inoue balloon catheter has been a popular device for the management of mitral stenosis. During the procedure several fatal complications, such as cardiac tamponade, perforation of a cardiac chamber, atrial septal defect, thromboembolism, mitral regurgitation and death have all been reported in the literature. There have also been several international reports regarding deformities of the Inoue balloon, but few reports in Korea. We recently experienced a case of an inflation failure of the distal portion of the Inoue balloon during a percutaneous mitral valvuloplasty in a 34 year old female patient with a tight mitral stenosis. To the best of our knowledge, a similar deformity of an Inoue balloon has never been reported in Korea.