A new bifoil balloon catheter has been used in the last 120 percutaneous mitral valvotomies carried out in our institution. The shaft segment between the two balloons of the bifoil catheter has been adjusted to the guide-wire diameter, allowing its introduction through a 14F sheath. This thinner shaft does not always offer enough back up to the balloons during inflation. An Inoue balloon replaced an unstable bifoil balloon in 5 cases of mitral dilatation failure due to balloon instability, regularly providing firm stability until full balloon inflation.