Aldrin-14C has been applied to soils under outdoor conditions in Germany (2.9 kg/ha) and England (3.2 kg/ha) and potatoes have been sown. At harvest, more than 60% of the total radioactivity recovered from the soil and plants was due to metabolites, mainly dieldrin and a group of hydrophilic products, of which the main compound was identified as dihydrochlordene-14C dicarboxylic acid (1,2,3,4,8,8-hexachloro-1,4,4a,6,7,7a - hexahydro-1,4-endo-methylene-indene - 5,7-dicarboxylic acid). Photodieldrin-14C was also detected in small amounts in the potato haulm from England, as were traces of photoaldrin-14C in both soils. The conversion of aldrin-14C was least in the upper soil layer and greatest in deeper soil layers (10-60 cm from surface) and in the plants. Only very low residues were detected in the deeper soil layers in England, whereas more radioactivity was found in the deeper soil samples in Germany. The leaching water of the experiment in Germany contained only dihydrochlordene-14C dicarboxylic acid (0.02 ppm).