Abstract: After evacuating and cleaning a discharge lamp, such as a fluorescent lamp, the lamp is dosed with mercury in the vapor phase. In particular, mercury vapor is introduced into the lamp at a predetermined pressure such that the vapor contained within the lamp corresponds to the required amount of mercury. To this end, the vapor pressure of mercury is controlled by controlling the temperature of the lamp and a reservoir of mercury in a pre-filled mercury container. Alternatively, a pressure regulator is used to directly control the vapor pressure of mercury at a sufficiently high temperature to maintain at least a portion of the mercury in the vapor state. Still another alternative method involves metering a fixed volume of mercury at a predetermined pressure. Finally, the discharge lamp is dosed with the remaining fill ingredients, e.g., at least one inert gas for a fluorescent lamp.