A downward illumination assembly for directing light downward from the ceiling area of a room. A lamp housing has an open lower end positionable adjacent an opening in a ceiling panel. A power supply module is removably supported in an installed position on the housing. The power supply module carries a lamp socket such that, when the power supply module is in the installed position, a lamp plugged into the lamp socket is disposed in a position to radiate light out the lower end of the lamp housing and through an opening in a ceiling panel that the housing is mounted on. The power supply module is removable interiorly of the lamp housing through the open lower end of the lamp housing.