We evaluated the in vivo performance of the Innovamedica pneumatic ventricular assist device (VAD), a new prototype of a simple, low-cost device for hospital circulatory support programs. We implanted the Innovamedica VAD in 6 sheep (weighing 55 to 91 kg). The inflow cannula was placed in the left ventricle, and the outflow cannula was anastomosed to the descending thoracic aorta. After heparinization (3mg/kg), we initiated the pump and monitored its hemodynamic performance for 6 hours. In a subsequent study we implanted the device for left ventricular support in two sheep for a 30-day period. We evaluated device performance based on implantation procedure, hemodynamic performance, and hematological impact. We monitored hematological and biochemical variables, and we assessed hemolysis. In the short-term experiments, the pumps maintained a mean blood flow of 4.4 ± 0.8 L/min. During support, mean arterial blood pressure was 76 ± 15 mmHg. The overall average concentration of plasma free hemoglobin was 5.11 ± 0.6 mg/dl compared with a baseline value of 4.52 ± 0.7 mg/dl. In the 30 day trials, mean blood output was 4 l/min ± 0.2, plasma free hemoglobin was 5.9 ± 4 mg/dl for the 30 day period excluding the first 48 hours. Warfarin/Aspirin anticoagulation was used after the first 72 hours with an average INR of 2.9 for the entire test period. Post-mortem showed no blood clots or any significant tissue damage to brain, lungs or kidneys. The devices operated without any significant adverse events in all of the experiments. The Innovamedica VAD was easy to implant and de-air and was found to be effective, reliable and biocompatible.