A maize crop was grown simultaneously under artificial shade and under natural shade from coconut palms. Under artificial shade, maize growth and development depended heavily on the radiation received. The more solar radiation was intercepted, the less the maize developed and yielded. Under our experimental conditions, where the only limiting factor was PAR, there was a simple linear relation between yield and PAR. Applying this relation to a coconut/maize intercropping system gave an estimated yield slightly higher than the actual harvest. This may be due to the difference between radiation interception by shading canvas and that obtained with a coconut cover, although the mean interception percentages were identical. A second explanation may be root competition between the two crops. Although this competition indeed exists, it was not detected in our experiment due to the excellent soil and climatic conditions, which prevented it from having any effect. Our experiment also showed that in maize, net assimilation response to PAR did not depend on the light treatment received.