However, only recently has it been shown that this generalization may extend to predation on the smallest hoofed prey of the wolf in North America, the white-tailed deer (_Odocoileus virginianus_). Pimlott _et al._ (1969) demonstrated a difference between the age structure of 331 deer killed by wolves during winter in Algonquin Park, Ontario, and 275 deer assumed to represent the actual population in the same area. Whereas only 13 percent of the deer from the population at large were estimated to be more than 5 years old, 58 percent of the wolf-kills were in this age category. We employed a similar analysis for deer killed by wolves in northeastern Minnesota, but used a more refined aging technique and included comparisons of the age and sex structures of various subsamples of wolf-kills. Whereas the Ontario research involved a prey population unlimited by man, our work was carried out on both a hunted population and on one relatively unhunted. Further comparisons were made between deer killed during periods of normal snow conditions and those taken during unusually high snow accumulations. The incidence of various abnormalities in wolf-killed deer was also compared with that in hunter-killed animals. The study was carried out in the Superior National Forest in northern St. Louis, Lake, and Cook Counties of northeastern Minnesota (fig. 1), in conjunction with other aspects of wolf research (see Mech _et al._ p. 1). [Illustration: _Figure 1.--The study area showing locations where wolf-killed and hunter-killed deer were taken. Line arbitrarily separates the hunted area from the wilderness area._] METHODS The investigation began in February 1966 and continued through March 1969; the basic objective was to examine as many wolf-killed deer as possible and compare their ages, sex, and condition with a large sample of deer from the population at large in the same area. Wolf-kills were examined only during December through March when they could be found from the air. Aircraft ranging in size from an Aeronca Champ to a Cessna 206 were used to fly over frozen lakes at altitudes up to 2,000 feet to locate wolves (fig. 2), wolf tracks, or kills (fig. 3). We often discovered kills by tracking a wolf pack. [Illustration: _Figure 2.--Wolves were located from the air, usually on frozen lakes. (Photo courtesy of L. D. Mech.)_] [Illustration: _Figure 3.--Wolf-kills were easily spotted from aircraft. (Photo courtesy of L. D. Mech.)_] During the winter of 1968-69 this method of finding kills was supplemented by radiotracking five wolves and their associates via aircraft (see Mech _et al._, p. 1). The latter technique resulted in increased discovery of inland kills.