Modular lighting bar mountable on a surface into which may be mounted one or more miniature light sources and an electrical supply line. The light sources can include light emitting diodes. The lighting bar has alternative single and two-component configurations that fix the position of the electrical supply line, and may be formed with a recess that receives an asymmetrically shaped electrical supply line in only one possible orientation. The ends of the lighting bar include mateable features for connecting additional bars. The bars may include recesses for receiving rigid members such as railing balusters, and optionally rotatable plugs to allow adaptation of the mounting bars to fit stair case railings with lighting and/or balusters.