A multi-agency trial was established to determine the impacts of commercial thinning on the growth, yield, and development of white spruce stands. The commercial thinning operation was completed using a Timberjack 1270 harvester and a Timberjack 1210B forwarder. The Forest Engineering Research Institute of Canada (FERIC) monitored the harvesting phase, determined the operational cost and productivity of the harvester and forwarder, determined the residual tree damage, and evaluated the effectiveness of a brushing crew in increasing the productivity of the harvester in areas with high densities of non-merchantable trees.