We have studied the long-term growth and development of seven infants who had been exposed during the foetal stage to ionising irradiation associated with percutaneous balloon mitral valvuloplasty between 1 April 1991 and 30 November 1993. We found that infants of mothers who underwent this procedure during the second and third trimester of pregnancy have normal long-term growth and development. This finding supports the arugement that percutaneous balloon mitral valvuloplasty using the Inoue balloon technique should be the procedure of choice for pregnant women who have severe mitral stenosis refractory to medical therapy.