Fifteen months after application of photodieldrin14C to soil (5 ppm of dry weight) in the open air, the following conversion products were identified by TLC, GLC, and mass spectrometry: the bridged isomer of dihydrochlordene dicarboxylic acid (1,7,8,exo-9,10,10-hexachlorotetracyclo[5.2.1.02,6.0 4,8]decane-3,5-exo,exo-dicarboxylic acid), amounting to about 0.5% of recovered radio-activity, a methoxylated derivative of this acid, amounting to about 0.5% of recovered radioactivity, and a bridged isomer of trans-4,5-dihydroxy-4,5-dihydroaldrin (3,exo-4,5,6,6,7-hexachloro-11,12-trans-dihydroxypentacyclo[6.4.0.0 2,10.03,7.05,9]dodecane), amounting to about 1% of recovered radioactivity.