Structural components of the forest canopy is one of several categories of information used in determining cross-country mobility from a military perspective. Canopy components of interest militarily include percent canopy closure, canopy height, stem spacing, and stem diameter. In this study high-resolution digital aerial photography was investigated as a potential data source for inferring the stem diameter component of the forest canopy. Crown diameter as measured on the aerial photography was selected as the surrogate parameter for predicting stem diameter. Crown diameters for individual trees identified on the imagery were measured in the field and on the photography. Field measurements of stem diameter were also collected. Equations predicting stem diameter from image estimates of crown diameter were developed and applied to selected trees within the imagery. Predicted stem diameters were compared to actual measurements made on the same trees.