To determine the intensity of quartz-tungsten-halogen light polymerization units in dental offices in El Salvador, Brazil.A team of researchers visited 100 offices in 2003. The team measured light intensity with a radiometer. The age and make of the units and the availability of light meters were recorded.One hundred twenty quartz-tungsten-halogen units were tested. Intensity ranged from 10 to 1,000 mW/cm2, with mean of 255.8 mW/cm2. Almost half (48%) of the units had values equal to or less than 200 mW/cm2. Their age ranged from 1 to 21 years. None of the offices had light meters.Clinicians should periodically monitor light intensity and carry out maintenance on their light polymerization units.