The anthracene method which is one of the techniques for assessing the light environment in ecological studies, is described with a view to utilizing in for practical applications. This method is based on the photochemical reaction of anthracene in an alcohol solution. The advantages of the method are that the light environment can be measured in many positions at the same time regardless of the weather conditions. The disadvantages are that the method tends to be time-consuming for the derivation of basic regression equations and the procedures preceding and following the field measurements, and that the chemical reaction is related to ultraviolet radiation, although the regression is usually derived based on the calculation of the photon flux density, illuminance or total irradiance. These characteristics are described along with the theory of the method. Practical procedures for laboratory and field measurements are described with some examples on the estimation of relative radiation in forests.