OBJECTIVE To evaluate and compare intrapulpal temperature rise with three different light-curing units by using a study model simulating pulpal blood microcirculation. METHODS The roots of 10 extracted intact maxillary central incisors were separated approximately 2 mm below the cement-enamel junction. The crowns of these teeth were fixed on an apparatus for the simulation of blood microcirculation in pulp. A J-type thermocouple wire was inserted into the pulp chamber through a drilled access on the palatal surfaces of the teeth. Four measurements were made using each tooth for four different modes: group 1, 1000 mW/cm(2) for 15 seconds; group 2, 1200 mW/cm(2) for 10 seconds; group 3, 1400 mW/cm(2) for 8 seconds; and group 4, 3200 mW/cm(2) for 3 seconds. The tip of the light source was positioned at 2 mm to the incisor's labial surface. RESULTS The highest temperature rise was recorded in group 1 (2.6°C ± 0.54°C), followed by group 2 (2.57°C ± 0.62°C) and group 3 (2.35°C ± 0.61°C). The lowest temperature rise value was found in group 4 (1.74°C ± 0.52°C); this value represented significantly lower ΔT values when compared to group 1 and group 2 (P  =  .01 and P  =  .013, respectively). CONCLUSIONS The lowest intrapulpal temperature rise was induced by 3200 mW/cm(2) for 3 seconds of irradiation. Despite the significant differences among the groups, the temperature increases recorded for all groups were below the critical value of 5.6°C.