The color-matching functions of six observers have been measured in the range of 400-700 nm in intervals of 10 nm using two modified Donaldson-type colorimeters at a luminance of 4.5 cd/m(2). A statistical study has been carried out to determine the interobserver variability (in our results), and the results of other authors using various representational color systems have been compared with ours. The most important findings are that, although a common mathematical mean cannot be found, the shape of the curves for the color-matching functions obtained in our laboratory for all the observers is very close to that of other authors, thereby implying that the overall color response of the human visual system is similar in all observers. In addition, the results show that, for the long wavelengths (around 600 nm), a great amount of desaturant primary (460 nm) is necessary, indicating possible rod intrusion under our experimental conditions.