Abstract: A metal-halide arc tube and lamp having improved uniformity of azimuthal luminous intensity and being particularly suited for navigational signal applications. The arc tube when operationally positioned about a vertical axis has a body which is substantially egg-shaped with the lower half of the body being more oblate than the upper half. During operation, the surface of the upper half of the arc tube body remains entirely free of metal-halide condensate so that no emitted light is blocked by condensate in any direction and nearly uniform azimuthal intensity is achieved. A heat-reflecting coating about the lower electrode prevents the formation of a condensate puddle about the lower electrode and relocates the condensate during operation to an area of the lower half above the coating and below the center of the arc tube.