Metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)-one] is an herbicide that can be effective in controlling many broadleaf weeds in soybeans. However, some soybean cultivars are sensitive to metribuzin and can suffer considerable damage (Wax et al., 1976). Previous research has established that a single recessive gene, hm, conditions the sensitive reaction of 'Semmes' (Edwards et al., 1976) and 'Tracy' (Kilen and Barrentine, 1983) to b metribuzin.