Modeling the balances of heat, water, vapor, and carbon dioxide within three-dimensional vegetation was tried. This model consists of three submodels: a model for turbulent flow within vegetation, a model for radiation transfer within vegetation, and a stomatal conductance model. This model was applied to a single tree. The numerical experiment resulted in the following : 1) A great deal of short wave radiation absorbed by leaves was released through transpiration. 2) The influence of long wave radiation on the energy balance within the tree was not negligible. 3) The sensible heat transfer due to water vapor flux from leaves hardly affected the energy balance within the tree. The fact indicates that the results from the turbulence model for dry air are almost equal to those of the turbulence model for moist air.