The composition, structure, and reproductive dynamics of two old-growth Douglas-fir (Pseudotsugamenziesii var. glauca (Beissn.) Franco) stands, located on opposing north and south aspects, were analyzed to reconstruct their past developmental patterns. Results indicate that the north aspect stand developed an even-aged structure initially and shifted to an uneven-aged structure over time. The theory of monospecific dominance by the climax species is supported on the north aspect as Douglas-fir maintains the highest importance value of all species present. The competitive exclusion principle appears inappropriate in this case as lodgepole pine (Pinuscontorta Dougl.), an intolerant, seral dominant, is reproducing successfully under the old-growth canopy. The south aspect stand has developed an uneven-aged structure and maintains it as harsh environmental conditions limit reproductive success to favorable microsites, precluding complete canopy closure.