Prior to 1979, most bear-inflicted human injuries in Yellowstone National Park (YNP) involved human food conditioned bears that were aggressively seeking human foods and injured people in the process. By 1979, human foods and garbage were no longer readily available to park bears and few human food conditioned bears remained in the population. During the 40 year period from 1979 through 2018, more than 118 million visits to YNP were recorded. These visitors spent over 26 million overnight stays camping in developed area roadside campgrounds, and over 1.6 million overnight stays camping in remote backcountry areas of the park. Although actual statistics are not available, thousands of menstruating women undoubtedly visited, hiked and/or camped within YNP over the last 40 years. From 1979 through 2018, 50 people were injured by bears (41 by grizzly bear, 6 by black bear, and 3 by bears where the species was not identified) within YNP, an average of only 1.3 bear-inflicted human injuries per year. Of these 50 injuries, 39 (78%) were men, and only 11 (22%) were women. Of the 10 incidents where women were injured, most (73%, n=8) involved surprise encounters with bears while the women were hiking, and were therefore not likely related to menstruation. One incident involved a female park ranger moving an injured bear that had been hit by a car, off of the roadway. In one incident a grizzly bear pulled a woman out of her tent at night and killed and partially consumed her. However, the woman was not menstruating at the time of the attack. In one incident a curious bear approached and bit a woman, but the woman was not menstruating at the time. There was no evidence linking menstruation to any of the 11 bear attacks on women. It is difficult to accurately compare the ratio of males to females that are injured by bears because the park does not keep records of visitor use in the park by gender. However, the bear-inflicted human injury data from YNP does not indicate any correlation between bear attacks and menstruation (Gunther and Hoekstra 1996).