To assess the role of blood flow in maintaining the patency of myocardial implants of the Vineberg type, hemodynamic measurements were made in two groups of animals immediately following revascularization. Perfusion of blood at systemic pressures into recently constructed arterial and venous myocardial implants resulted in no blood flow from implant to myocardium in five of ten experiments. Perfusion of myocardial implants at a constant flow rate of 3.8 ml of blood per minute resulted in suprasystolic implant pressures and large myocardial hematomas in all dogs. The absence of immediate implant blood flow at systemic perfusion pressures and the development of myocardial hematomas following low volume perfusions suggest that flow from implant to myocardium is not an important determinant of immediate implant patency and that myocardial revascularization has no immediate therapeutic value.