Abstract: A parabolic reflector lamp is provided wherein lamp efficiency is improved by more substantially approximating the shape of a complete parabola at the inner reflective surface. In a first embodiment, the heat shield is placed at the mouth of the opening at the base of the lamp, thereby “filling in” the opening and substantially completing the parabolic shape of the reflector. In a second embodiment, the opening at the base of the lamp is narrowed to minimize its cross-sectional area and maximizing reflective surface area. In a third embodiment, the glass shell of the lamp is provided in a two-piece configuration, allowing the size of the hole through the base of the glass shell to be reduced. The openings required to accommodate electrodes (and an exhaust tube in sealed lamps) are located in a second cup-shaped piece attached via a flange to the main body of the glass shell.