Studies have established that advanced turboprop (prop-fan) equipped aircraft will reduce fuel consumption by 15 to 30 percent compared to aircraft equipped with high-bypass turbofan engines of equivalent technology. A reduction in direct operating costs of approximately 10 percent has been identified for commercial aircraft as well as approximately a 20 percent lower gross weight airplane for long endurance military missions. The prop-fan propulsion system is being investigated as part of the NASA Aircraft Energy Efficiency program which includes both analytical studies and experimental tests. The experimental work encompasses performance and acoustic wind tunnel tests on several prop-fan models. The prop-fan technology status is reviewed in the major areas of performance, installed effects, cabin noise, blade structure and maintenance cost. Also, future activities required to complete the technical validation of prop-fans are described.