This research examined the effect of immersion in glutaraldehyde-based cold sterilizing solutions on the ability of light-curing tips to transmit a standardized light intensity. Five commercial cold sterilizing solutions were selected, based on their classification: neutral (Cetylcide-G, 3.2%), acidic (Banicide, 2.0%), or alkaline (Cidex Plus, 2.5%; Cidex 7, 3.4%; and Sporicidin, 0.5 %). Distilled water was used as the control. The light intensity transmitted through 24, 8-mm-diameter curing tips of similar type was determined by aplying a standardized intensity (500 mW/cm to the second power). Three tips were placed into each type of solution. The percentage of preimmersion intensity was determined at periodic intervals until all tips had received a total of 1,000 hours of immersion. After 1,000 hours; immersion, light transmission decreased significantly more in tips subjected to Cidex 7 than in tips subjected to all other treatments, which were all equivalent to the water control (an average increase of 1.5% over preimmersion values). The de crease in intensity seen with Cidex 7 averaged 49% and could not be totally recovered after use of sonventional tip-polishing methods. Reduction in light levels could not be correlated with the pH of the sterilizing solutions.