Recently, simple radiometers for measuring the intensity of dental curing lights have been introduced. This study examined the relationship among light intensity measurements by three radiometers, distane of curing tip from composite resin, and resin polymerization (as indicated by microhardness). Light intensity measurements, which decreased with increasing distance from the curing tip, were strongly correlated with composite resin hardness. Reduced light intensity produced softer composite re sin particularly on the bottom of specimens (2-mm depth). The different radiometers provided similar indications of the changes in light intensity at various curing distances.