Two thousand five hundred and sixty-two participants in a college intramural basketball program were studied during two successive intramural “seasons” with regard to the frequency of ankle and knee sprains, as related to the use of external ankle support. The influence on injury rates of high- and low-top shoes and the use of prophylactic ankle taping were examined, and an additional group of players was supported with a disposable elastic material during the second season of study. The use of both high-top shoes and prophylactic ankle taping appeared to decrease the frequency of ankle sprains. This decrease was particularly marked in those subjects who had suffered previous ankle sprains. The size of the additional group was too small to permit valid comparisons. No increase in the frequency of occurrence of knee sprains was observed to result from the use of high-top shoes and/or prophylactic ankle taping.