Leaching of 14C-ring-labeled technical trifluralin from the top 5 cm of soil was followed in a microlysimeter experiment under outdoor conditions. Leaching of water residues from soil was low and represented 2.2, 5.4, and 6.7% of the applied radioactivity after 6, 12, and 18 months, respectively. Two degradation products, called A and B, were clearly detected and represented about 80 and 10% of the leached radioactivity, respectively, whereas other degradation products accounted for about 10%. Trifluralin itself was detected in the leachate only between 3 and 6 months. Cumulated amounts of leached trifluralin were only 1% of the leached radioactivity after 1 year: i.e., 0.06% of the applied product. A second-year microlysimeter experiment demonstrated that the use of formulated trifluralin had no influence on leached amount and content.