Pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] degradation in three soils did not follow first-order kinetics but could be described by a quadratic model. Degradation increased as soil temperature increased in the order 10, 20, 35, and 30C. The rate was the same as 75 and 100% field capacity but slower at 50%. At the same temperature and soil moisture the influence of soil type was small. Based on chemical analysis of soil from field and laboratory studies, the half-life was approximately 47 days. Based on biological analyses of soil, the half-life was 78 to 111 days.