Since 1986, ENTECH and NASA Lewis have been developing refractive solar concentrators for space applications. These Fresnel lens concentrators can be configured as either point-focus dome lenses or line-focus cylindrical lenses. Small point-focus or line-focus lenses can be used to concentrate sunlight onto solar cells in space photovoltaic (PV) arrays. Large point-focus lenses can be used for high solar flux applications. In March 1997, a NASA Phase I SBIR program was initiated to develop ultralight inflatable lenses of both the line-focus and point-focus types. Special program emphasis is being placed on large point-focus lenses for various high-concentration applications, including solar dynamic (SD) power, alkali metal thermal energy conversion (AMTEC), thermophotovoltaics (TPV), and solar thermal propulsion (STP). Key outputs of the Phase I program include conceptual designs, optical performance predictions, micrometeoroid puncture analyses, manufacturing process identification, and functional prototype hardware. This paper summarizes the key results of the Phase I program, leading to the conclusion that inflatable dome lenses will provide excellent high-concentration optical performance, unequaled shape error tolerance, extremely low mass/aperture area ratio, proven manufacturability with space qualified materials, and small make-up gas requirements to maintain inflation on-orbit.