Two eddy correlation systems, each composed of a CSAT3 and a LiCor 7500, have been deployed at the Elora Research Station since July, 2000. These systems have been run side-by-side, vertically aligned, on opposite sides of the tower, and in adjacent plots. This data has allowed us to examine quantitatively several aspects of eddy correlation flux estimates. In particular, we report on error estimates, spectral corrections and quantify the shadowing effect. Agreement between the two systems when run side-by-side was excellent, while shadowing led to a consistent underestimate of approximately 30--40%.