Disclosed herein are herbicidal compositions comprising a synergistic herbicidally effective amount of (a) penoxsulam or an agriculturally acceptable salt thereof and (b) acetochlor or an agriculturally acceptable salt thereof. Also disclosed herein are methods of controlling undesirable vegetation, which comprise applying to vegetation or an area adjacent the vegetation or applying to soil or water to prevent the emergence or growth of vegetation (a) penoxsulam or an agriculturally acceptable salt thereof and (b) acetochlor or an agriculturally acceptable salt thereof, wherein (a) and (b) are each added in an amount sufficient to produce a synergistic herbicidal effect.