The amounts of ^(14)CO₂ evolved during the ^(14)C-bentazon aging in soil for 3 and 6 months were 6.1 and 14.8% of the original radioactivity, respectively. The presence of earthworms in soil tended to increase the uptake of ^(14)C-bentazon by the roots of rice plants, even if it was not statistically significant. The evolution of ^(14)CO₂ from ^(14)C-bentazon in soil increased in the presence of rice plants and earthworms compared with in the absence of them. The uptake of ^(14)C-bentazon residues by rice plants decreased remarkably with increasing the aging period within the limit of 3 months both in the absence and presence of earthworms, but there is not much difference between 3-month-aging and 6-month-aging. Much larger amounts of ^(14)C-labelled compounds were translocated to the shoots, compared with the data from a previous investigation using maize plants. The amount of non-extractable bound residue increased remarkably with the aging period up to 3 months. The polarity of the compounds extracted from soil increased with the aging and the growing of rice plants, indicating the formation of some polar metabolites.