The light output of a compact fluorescent lamp is enhanced by providing the envelope with a phosphor-coated partition assembly which has a plurality of panel segments that divide the envelope interior into a series of interconnected sectors and also define a centrally-located core chamber that is closed to the discharge. The size of the core chamber is correlated with the size of the envelope in such a manner that the discharge is displaced from the center of the envelope toward the phosphor-coated walls thereof, thus reducing losses due to the "trapping" of light deep within the envelope interior and concurrently increasing the relative amount of ultraviolet radiation that reaches and excites the phosphor coating on the envelope wall. The efficacy of the partitioned fluorescent lamp is accordingly increased. The size-correlation is rather critical and must be such that the maximum cross-sectional dimension of the core chamber at a given location is from about 25% to about 85% of the maximum cross-sectional dimension of the envelope at the same location and optimum results are obtained when this parameter is around 50%. The improved fluorescent lamp is thus especially adapted for use as a substitute for incandescent lamps in various types of lighting fixtures where space is limited and a light source of high brightness is required.