The aim of this study was to evaluate the characteristics of new-generation light-emitting diode (LED) units in comparison with the conventional tungsten-halogen, plasma arc, and first-generation LED units reported in our previous study. The irradiance of light from new-generation LED units, the temperature rise of the bovine enamel surface, and the depth of cure of composites exposed to each unit were investigated. The irradiances in the range 400-515 nm emitted from the new-generation LED units were greater than those from the first-generation LED units. The temperature increase was 15-25 degrees C for new-generation LED units compared with a typical value of 5 degrees C for the first-generation LED units at 10 s of irradiation. The relationship between the depth of cure and the logarithm of total exposure energy suggested that LED units can cure light-cured composite resins more efficiently than tungsten-halogen or plasma arc units.