The toxicity of 1,1'-dimethyl-4,4'-bipyridinium ion (paraquat) in soil can be related to the degree of bonding strength to the soil aggregates. Tightly bound material is unavailable to plants, while loosely bound material can be potentially available to plants. On the basis of growth of corn (Zea mays L., var. Golden Cross Bantam) and beans (Phaseolus vulgaris L., var. Idaho 1-11) in sand, loamy sand, loam, and muck treated with paraquat, it is concluded that planned and careful application would not lead to accumulation of lethal dosages in medium to heavy soils.