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In this study 16 different light curing units, available on the Swiss market, were tested for their features, radiant power and light distribution across the face of the curing tip and components like integrated radiometer, timer and cooling device. The basis of this study was the test protocol published in the november edition (11/1999). The features of the light curing units differed from one another. The Optilux 500 had all conceivable features that it could be designated the standard in features. If all these technical options are necessary has to be decided by the consumer. However, the components such as the timer, radiometer and voltage stabilizer are important because they influence the time of irradiation and the radiant power. The radiant power (mW) i.e., the radiance (mW/cm2) were measured in 2 spectral areas which are important for visible light polymerisation. The absolute values for the standard curing tip at a voltage of 230 V lay between 143.4 and 389.7 mW for the wavelengths between 400-520 nm and between 17.7 and 41.8 mW for the wavelengths between 462-472 nm. The resultant specific radiance values were between 268.3 and 862.6 mW/cm2 in the broad spectrum of 400-520 nm and 33.5 and 95.4 mW/cm2 in the narrow spectrum of 462-472 nm. Where the standard curing tips were replaced by guides with other diameters, tips with larger entrances showed more radiant power, light guides with smaller exits also showed more radiance. Turbo tips have larger entrances than exits and therefore combine both positive effects. The intensity wasn't distributed equally across the face of the curing light guide. Characteristically there was a concentric distribution of the intensity, with the maximum found in the centre and a decrease to the margin. Corresponding to the radiance values, curing light tips with decreasing diameters showed more homogeneous distribution patterns. Only Turbo tips showed worse distribution. Comparing the light intensity at a voltage of 207 V and 244 V to the normal voltage of 230 V it was found that not all curing units had an integrated voltage stabilizer. Just 9 out of the 16 tested units had an integrated radiometer. Comparison of the evaluated radiance values to the values given by the integrated radiometer revealed an agreement in just two cases. The marginal values, programmed by the manufacturer varied between 70 and 300 mw/cm2 and lie therefore, too low.