Severe intravascular hemolysis developed following aortic valve replacement with a No. 17 Björk-Shiley prosthesis in a patient with a diminutive aortic annulus. At reoperation, a residual gradient of 54 mm. Hg and no evidence of perivalvular leak were found. A second left ventricular outflow tract between the apex and the supraceliac abdominal aorta was fashioned with a special rigid (Pyrolite) prosthesis and a heterograft valved composite conduit. The gradient was reduced to 5 mm. Hg and hemolysis was reversed. We have now created double-outlet left ventricles for primary or recurrent left ventricular outflow tract obstructions of various etiologies in 13 other pediatric and adult patients. The longest follow-up is approaching 18 months. All gradients have been sharply reduced and all patients are asymptomatic.