Nightlight counts and daytime observations were utilized in the Great Smoky Mountains National Park to measure the effects of hemorrhagic disease on a high density white-tailed deer (Odocolieus virginianus) population. Deer utilization of 1,846 acres of pasture in the Cades Cove area appeared to be greatest during February, 1971. Following the availability of spring browse, the number of deer utilizing the pastures stabilized at approximately one deer per ten acres until the die-off. During the period of mortality (August through October) utilization of pastures by deer decreased by 84 percent. This decrease in utilization closely corresponds with percent mortality observed under experimental infection with the epizootic hemorrhagic disease virus in deer. Utilization of pastures nine, twelve and twenty-four months post-dieoff was similar to pre-dieoff use. The above and other data indicate that the disease was probably restricted to the Cades Cove area, that vacant niches were filled by animals from peripheral areas and that decreased utilization of pastures during the die-off was due to mortality caused by a hemorrhagic disease. A total of eleven cattle were reported to have died prior to and during the deer die-off period and exhibited gross lesions similar to those of the deer. The possibility of resistance by cattle to the disease and inters pecific transmission of the disease are cited.