Results of an energy balance study conducted in 1974 at Montmorency, Quebec, are reported. The energy balance components of a balsam fir (Abiesbalsamea L. Mill.) canopy, evaluated for 7 sample days, show marked differences in energy partitioning. The days are separated into two groups. The difference in the energy balance between the groups is related to the value of volumetric soil moisture in the top 0.1 m of soil. On days when the volumetric soil moisture is 36% or more, potential evapotranspiration conditions are operative, and evapotranspiration is the largest term in the energy balance. Also, it is strongly coupled to net radiation. Whenever the volumetric soil moisture is 32% or less, potential evapotranspiration conditions are not operative, and characteristically, the sensible heat flux to the air is the same or slightly larger than the evapotranspiration. Both fluxes are strongly coupled to the net radiation. For all hours the soil heat flux is negligible. For potential evapotranspiration, the equation developed by Priestley and Taylor is tested. Under potential evapotranspiration conditions the equation, with α = 1.26, estimates daily water loss to within 3%. The Bowen ratio solution to the energy balance is used as the standard for comparison. Whenever the volumetric soil moisture is 32% or less, α is variable and less than 1.26. The minimum value found is 0.67.