The soil residual herbicide bioassay has been commonly used to determine the potential for crop injury following the use of residual herbicides. In spite of the bioassays use, there has been very little information available on the accuracy of the bioassay. In order to assess the level of accuracy, two independent studies were conducted; the first by AAFC, and the other by BASF. Existing sites containing soil residual herbicides were used, and field results on these sites were compared to the greenhouse bioassay result. The AAFC study showed low corroboration, and a high number of false positives, while the BASF study showed low corroboration and a high number of false negatives. Both studies indicated that the level of accuracy of the bioassay was low, and was not predictive of the result found in the field.