Root density and mortality were determined in 30 healthy western white pine (Pinus monticola Dougl.) stands ranging from 20 to 160 years old. Similar determinations were made in 16 stands of the 60- to 80-year age class affected by pole blight, a disease of unknown cause. Various physical soil characteristics were measured in 26 healthy and diseased stands of the 60- to 80-year age class in conjunction with the root study. Both rootlet mortality and density in the upper 1 foot of soil in the 60- to 80-year age class are significantly correlated with the available water storage capacity in the soil depth occupied by a major portion of the root system. The available water storage capacity is dependent upon effective soil depth. As the severity of pole blight increases, rootlet mortality increases and available water storage capacity and effective soil depth become less. These results indicate an edaphic relationship to the pole blight disease.