Technical Abstract: Meadow foxtail is a rhizomatous grass widely grown for hay and pasture in wet meadows of the western United States and Canada. I compared the influence various rates of these two sulfonylurea herbicides on meadow foxtail biomass. Treatments of 0.035, 0.070, 0.105, and 0.140 kg/ai ha of chlorsulfuron or metsulfuron-methyl rates and a non-treated control were applied at each of two sites in October 2003. Treatments were replicated 4-times at each site and arranged in a randomized complete block design and sampled in July 2004 and 2005. Meadow foxtail biomass depended on site (P=0.001) or year (P=0.001), but not herbicide treatment (P=0.182). No biomass production losses resulted from applying up to 0.14 kg/ha of either chlorsulfuron or metsulfuron-methyl on meadow foxtail, even in relatively high pH soils.