Technical Abstract: There are multiple tools available for testing for glyphosate resistance. Whole plant screens, whether in the field or greenhouse, should be used as an initial method to determine if a biotype is glyphosate resistant. Screening for resistance using seedling assays such as in Petri plates, sand culture, plant parts, and others are more rapid than whole plant screens, but they are limited in their applicability. They will only detect resistance if it is manifested at the seedling stage. However, for screening large numbers of biotypes, seedling based screens may provide an initial way to rank the level of resistance in each biotype. The use of physiological based screens, such as shikimate accumulation, or loss of chlorophyll may be more rapid than either greenhouse or seedling based assay and they can be relatively high throughput, so large numbers of biotypes can be screened quickly. DNA/RNA based assays could be a very robust way to screen large populations for glyphosate resistance if the mechanism of resistance is due to either differential expression of EPSPS or a mutation in EPSPS. The use of 14C-glyphosate is essential for determining if reduced translocation is the mechanism of resistance.