Miller, R. T., Soltani, N., Robinson, D. E., Kraus, T. E. and Sikkema, P. H. 2012. Soybean (Glycine max) cultivar tolerance to saflufenacil. Can. J. Plant Sci. 92: 1319-1328. Six field studies were conducted over a 2-yr period (2009 and 2010) at three Ontario locations to determine the sensitivity of 12 glyphosate-resistant soybean cultivars to saflufenacil applied preemergence (PRE). The level of crop injury was dependent on environmental conditions shortly after application. When soybean emergence was delayed due to cool, wet conditions following planting, 52 and 59 g a.i. ha^-1 of saflufenacil resulted in 10% injury 1 wk after emergence (WAE) in cultivars OAC Hanover and RCAT Matrix, respectively. In the other environments, greater than 200 g a.i. ha^-1 of saflufenacil was required to induce the same level of injury at 1 WAE. Injury decreased with time; however, the more sensitive soybean cultivars were unable to recover from early-season injury sustained under adverse environmental conditions. A hydroponic bioassay was developed to screen differences in soybean tolerance to saflufenacil. OAC Hanover was more sensitive than all the other cultivars in both field and hydroponic testing (P<0.05). OAC Hanover yield was reduced regardless of environmental conditions. Under cool, wet conditions, 22 g a.i. ha^-1 of saflufenacil resulted in a 10% yield reduction, while 46 g a.i. ha^-1 was needed under warm dry conditions. All other cultivars required between 82 and 146 g a.i. ha^-1 to obtain the same level of yield reduction. This research demonstrates that there is a difference in soybean cultivar sensitivity to saflufenacil applied PRE.