The objective of this study was to measure the between-trial variability of the center of pressure pattern integral (COPPI) at the shoe-floor interface and within the shoe. Ten trials of the COPPI were recorded simultaneously at the shoe-floor interface and within the shoe as ten subjects walked over ground in standardized footwear and with two types of foot orthoses. While the results showed that the within-shoe shoe-only and soft orthoses conditions caused the greatest decrease in the COPPI, it was extremely inconsistent-between trials, whether measured at the shoe-floor interface or within the shoe. This suggests that the COPPI is not an acceptable method of assessing the effectiveness of foot orthoses.