A Thoratec left ventricular assist device (LVAD) was used to support a 7-year-old 17-kg boy with viral cardiomyopathy for 23 days before heart transplantation. The boy is still living more than 1 year posttransplant, and functional except for some spastic paresis of the left hand, a residual from a stroke during device support. He is the smallest person to be supported with this device. We discuss techniques for using the Thoratec in children. (C) 2001 by The Society of Thoracic Surgeons.