Red(R) light was the most effective night-break for inhibiting flowering and the effect of red light could be reversed by a brief subsequent exposure to far-red(FR) light in chrysanthemum. On the other hand, different electric lamps are frequently used as the light sources for growing plants to supplement low natural light or for photoperiodic control of flowering. In the present experiment, the effect of different light sources on flower initiation of chrysanthemum (Dendranthema grandiflora Tzvelev) cv. Long day leaf number increased and time to flower bud decreased in the order of incandescent, fluorescent, metal halide, and high-pressure sodium lamps. Advanced flower bud initiation and decreased long-day leaf number under fluorescent lamps compared to incandescent lamp are attributed to the high R/FR ratio (6.43) and φ value (0.84) of fluorescent lamps. Fluorescent, metal halide, and high-pressure sodium lamps had similar levels of φ(0.83±0.01) and blue plus red light composition over photosynthetically active radiation (0.46±0.02) but their light intensities varied from 7.3 to 160.6 μmol·m-2·s-1.