Persistence of BAY SMY 1500 and chlorsulfuron during storage for 0 to 6 mo at room temperature in air-dry clay loam soil with pH 7.6 and sandy loam soil with pH 6.6 was determined with conventional wheat bioassay procedures. BAY SMY 1500 had predicted half-lives greater than 6 mo in both soils. Half-lives of chlorsulfuron were 6.0 and 3.2 mo in the clay loam soil and sandy loam soil, respectively.