The influence of environmental factors on the timing of the rut and the length of the gestation period in the white-tailed deer (Odocoileus virginianus) is poorly understood. Since 1965, we have been recording population data for a confined herd of whitetails in Virginia. Although the peak of the fawn drop appears to be rather consistent from year to year, some variation has occurred during our 8 years of study. This variation led us to examine some factors which might bear on the time of fawning. Environmental factors as influences on deer reproduction have been studied by several wildlife researchers. McDowell (1970) reported on conception dates of whitetails and concluded that light duration has a powerful influence on breeding periodicity. Cheatum and Morton (1946) found regional differences in the onset of mating between northern and southern New Yark deer. These differences were believed to be due to latitude, altitude, light intensity, temperature; and other external influences. Cheatum and Morton cited Bissonette (1941), who observed that the fall breeding season may be hastened by keeping goats in dim light. Severinghaus and Cheatum (1956) discussed the possible influences of light and temperature on the onset of breeding among whitetailed deer and in addition, referred to similar work done on other species. Sadlier (1969) reviewed the effect of temperature, daylight, and nutrition on the breeding cycles of various wild and domestic species. Verme (1965), in his examination of reproduction in penned whitetails, reported that deer on a high plane of nutrition began breeding 15 days earlier than deer on a low plane of nutrition. One-third of the well-fed deer had bred before the poorly fed deer began to breed. Additionally, well-fed deer averaged 6 days' shorter gestation period. These combined factors resulted in the average fawning date being 12 days earlier in the well-fed deer. Thanks are due personnel of the Radford Army Ammunition Plant for cooperation in this study. Special gratitude is due Lt. Col. Virgil E. Moore, Jr., Commanding Officer, and graduate students R. Petcher, J. Sandt, F. Kreitzer, R. Poux, J. Gavitt, and C. Smart.