The objective of this study was to assess the curing efficiency and heat generation of two high-intensity halogen lamps, the Astralis 10 HIP (1100 mW cm(-2)), and Optilux 501 Boost (1000 mW cm(-2)) in curing three resin composites (InTen-S, Tetric Ceram, and Filtek Z250). It was expected that the two lamps, having similar irradiance would give rise to the same curing efficiency and heat generation. The curing efficiency was evaluated by Vickers hardness and depth of cure measurements. Heat generation in the resin composites was studied in standardized restorations using a thermocouple. No significant differences were observed in curing efficiency between the two lamps for the three resin composites. The temperature rise in the composites during curing was between 11.2 degrees C and 16.2 degrees C. At subsequent irradiation, after the composites had been cured, the temperature rise was between 8.2 degrees C and 12.1 degrees C. The Optilux 501 generated, in all cases, less heat than the Astralis 10. This was not expected based on the irradiance, but could be accounted for by the differing spectra.