Abstract Studies of the comparative micrometeorology of two plant communities, a field of wheat and a forest of Pinus radiata, are described. They were made over a period of four weeks in the spring, in the region of Canberra, where both communities grow under natural rainfall in similar aerial environments. Components of the energy balance are compared. For a given short-wave solar radiation intensity, quite large differences existed between the communities in net radiation, evaporation, photosynthesis and soil heat flux. The first three of these were greater for the forest, and the last was smaller. The data suggested that not only was net radiation generally higher for the forest, but also more of the available energy was partitioned into latent heat. Approximate calculations of mean foliage temperatures were made from the radiation balance of both communities. These indicated that, in general, foliage temperatures of the forest were close to, or even less than, air temperatures, while those of the wheat field were several degrees higher. The calculations provided independent evidence for greater proportional evaporation from the forest than the wheat field. In view of these differences, some comments are offered on the concept of potential evapotranspiration. Because of differences in surface roughness, eddy diffusivities were generally almost an order of magnitude greater over the forest than over wheat. Since gradients of the various entities were correspondingly smaller over the forest and therefore harder to detect, it was sometimes difficult to arrive at satisfactory flux estimates for that community. In terms of productivity, photosynthesis per unit of evaporation was greater for the forest, despite its greater water use.