Subaortic stenosis is a complex lesion that often presents in older children and adolescents. A clear depiction of the lesion is required for optimization of surgery. Due to the large size of these patients, is not always possible from surface echocardiography. Intraoperative multiplane echocardiography (MTEE) has been performed at our institute in older children for several different congenital heart lesions including many patients with subaortic stenosis. A retrospective analysis of our experience with MTEE in patients with subaortic stenosis was performed to assess its usefulness in the preoperative diagnosis and postoperative assessment of repair. Our results show that intraoperative MTEE was useful preoperatively by correcting or confirming suspected diagnosis, and giving additional details of the lesion in many patients. Postoperatively, MTEE was highly useful in the assessment of repair. We strongly recommend the use of intraoperative MTEE in older children and adolescents with subaortic stenosis. (ECHOCARDIOGRAPHY, Volume 13, November 1996)