One year after the last of six annual applications of 3-(p-chlorophenyl)-l,l-dimethylurea (monuron) at 2.4, 3-(3,4-dichlorophenyl)-l,l-dimethylurea (diuron) at 2.4 and 7.2, and 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) at 1.0 and 3.0 lb/A in a furrow-irrigated vineyard on Warden silt loam, a bioassay using oats (Avena sativa L., var. Kanota) as the indicator showed that 1.6, 2.8, 10.6, 0.6, and 2.0 lb/A, respectively, remained in the surface 12 in of soil. Of the total, 62 to 89% was located in the surface 2 in and 86 to 100% was in the surface 4 in. Three years after the last of four annual applications of monuron at 7.2 lb/A, 0.8 lb/A remained in the surface 12 in.