A production and cost study for the Koller K300 skyline yarder operating on an Appalachian timber sale was undertaken to document the yarder’s performance, to identify predictors of yarder performance, to evaluate the impact of corridor dimension on machine productivity, and to estimate direct harvesting costs. The average yarding cycle lasted 5.10 minutes and produced 36.1 cubic feet of timber. Lateral yarding consumed an average of 59 percent of the yarding cycle and included 71 percent of the operating delays observed. Log hangups account for 59 percent of the operating delays. Reliable prediction of the yarding cycle time is difficult due to wide variability in the observed times. The best model found for predicting the duration of the yarding cycle uses yarding distances and lateral yarding distance as independent variables. The lateral yarding element is the least predictable element of the yarding cycle. Simulation analyses were used to investigate the effects of changing corridor dimension on average hourly yarding productivity in light of machine setup time. Corridor widths of 52 feet resulted in significantly less production than widths of either 104 or 208 feet when yarding road changes were assumed to require two hours. Corridor lengths of 208 feet were significantly less productive than lengths of 416 or 624 feet. No significant difference in productivity was found for the three corridor lengths when road changing time was reduced to one hour. Again, the 52 foot corridor widths were less productive. Estimated direct harvesting costs (on board truck) are given for two system configurations and three utilization levels. The estimates range from $22.21 per cord to $37.14 per cord. / M. S.