Field experiments were conducted near Manhattan, KS in 2005 and 2006 and Sabetha, KS in 2005 to determine the efficacy of S-metolachlor tank-mixed with fomesafen or metribuzin as an element in the control of common waterhemp in soybean. Preemergence treatments included S-metolachlor fomesafen at 0.91 0.22, 1.21 0.28, 1.52 0.36, and 1.82 0.43 kg ai ha⁻¹ (kg active ingredients per hectare) and S-metolachlor metribuzin at 2.42 0.59 kg ai ha⁻¹. These treatments were applied alone or followed by a postemergence glyphosate application at 0.88 kg ha⁻¹. Common waterhemp control with S-metolachlor fomesafen was greater than 88 and 60% at 2 and 8 WAT (Weeks After Treatment), respectively at Manhattan in 2005. However, S-metolachlor fomesafen, regardless of the rate, gave complete common waterhemp control 2 WAT and greater than 95% common waterhemp control through 8 WAT at Sabetha. In 2005, S-metolachlor metribuzin controlled 59 and 91% of common waterhemp 8 WAT at Manhattan and Sabetha, respectively. By 8 WAT, glyphosate applied after preemergence treatments improved common waterhemp control; however, no additional control was achieved with the postemergence glyphosate applications at Manhattan in 2006 and Sabetha in 2005. This research showed that early season control of common waterhemp can be achieved with preemergence application of S-metolachlor fomesafen at 1.52 0.36 kg ha⁻¹ with or without a postemergence application of glyphosate.