Foot orthotic devices (FOD) are often used to treat excessive pronation and related problems of runners. In order to assess the effectiveness of FOD, 29 runners who used FOD were filmed on an outdoor track during three conditions: 1 ) barefoot, 2) running shoe, and 3) running shoe plus FOD. The barefoot data were not used because of marked variability. Comparison between the shoe and FOD conditions showed that only two of the six variables were statistically significant at the 0.05 level. Both the maximum angle of pronation and percentage of support time in pronation on the left foot were significantly decreased in the FOD trial. No significant differences were found between the shoe and FOD conditions for the other four variables (pronation velocity on both feet, maximum angle of pronation on the right foot, and percentage of support time spent in pronation on the right foot). The variability of these results support the conclusion that the type of FOD used in this study have questionable effectiveness in the treatment of excessive pronation. J Orthop Sports Phys Ther 1982;4(2):86-90.