These studies were conducted in the laboratory on two soils at two temperatures to define the rate of degradation and the associated rate law for trifluralin (α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine), benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), and 2,6-dinitro-N-(3-pentyl)-α,α,α-trifluoro-p-toluidine (hereafter referred to as Unnamed). Rate of degradation was directly correlated with temperature and moisture content. First order kinetics adequately described the rate of degradation at 15 C, but the simple first order assumption was not sufficient to describe degradation at 30 C. The implication of our interpretation is that at 30 C two rate processes may operate in the soil degradation of these three dinitroaniline herbicides. The data show an initial rapid first order rate of degradation with a subsequent change to a slower first order process. First half lives ranged from 0.4 to 1.8 months at 30 C and were consistently lower in a loam than in a sandy loam soil.