The effect of light intensity on height growth of trembling aspen greenwood cuttings was observed under two temperature regimes. Reduction of light intensity from 1,700 to 500 ft-c was accompanied by a significant reduction in height growth at 76F (day) - 71F (night). At 70F (day) - 66F (night), however, no significant difference in height growth due to light intensity was observed. Results are interpreted in terms of the relationship between photosynthetic accumulation and respiratory loss of energy as affected by temperature and light.