A metal halide discharge lamp which essentially permits disusing mercury is
provided. The metal halide discharge lamp comprises a refractory and
transparent hermetic vessel, a pair of electrodes fixed to the hermetic
vessel, and a discharge medium sealed in the hermetic vessel and
containing a first halide, a second halide, and a rare gas. The first
halide is a halide of a metal which achieves a desired light emission. The
second halide has a relatively high vapor pressure, being at least one
halide of a metal which is unlikely to emit a visible light compared with
the metal of the first halide and acts as a buffer gas.