For the formation of aged pretilachlor soil residues, soils treated with [^(14)C]-Pretilachlor(specific activity : 1.42 MBq/㎎) were incubated aerobically at 21±1 ℃ for 2.5 and 5 months. Throughout the aging in the dark, moisture was replenished weekly and kept at 50% of the maximum water-holding capacity of the soil. The amounts of ^(14)CO₂ evolved during the periods of 2.5 and 5 months were 2.18 and 4.63%, respectively, of the originally applied radioactivities. Rice plants were grown in soils containing various Pretilachlor residues (5 μCi/1.5 ㎏ soil) in a specially devised microecosystem. Three kinds of Pretilachlor residues include (1) Freshly treated (T-1), (2) 2.5-month aged (T-2), (3) 5-month aged Pretilachlor residues (T-3). Mineralization of [^(14)C]-Pretilachlor to ^(14)CO₂ during the 42 days` growth period in T-1, T-2, and T-3 was 0.2, 0.9, and 1.2%,respectively. The amounts of [^(14)C]-Pretilachlor absorbed by rice plants were 5.1 (root, 2.8 and shoot, 2.3%), 6.5 (root, 3.5 and shoot, 3%), and 5.8% (root, 3.1 and shoot, 2.7%), respectively, in T-1, T-2, and T-3.