A 14C-labeled sample of 2,6-dichloro-4-nitroaniline (DCNA, Botran) was incubated in flooded soil that had been amended with D-glucose (1%, w/w). After 3 days the amount of DCNA that could be recovered from the soil decreased to 7% and to 3% after 9 days. Evolution of radioactive carbon dioxide could not be detected even after the 9-day experimental period. Much of the radioactivity (ultimately 65%) could not be removed from the soil sample by extraction with an acetone-water solution. The major metabolite that was extractable from soil was identified as 4-amino-3,5-dichloroacetanilide (ADCAA).The expected metabolic precursor of ADCAA, 2,6-dichloro-p-phenylenediamine (DCPD), was also isolated from the extraction solution. A third compound isolated from soil appeared to be formed by the oxidative dimerization of DCPD. This same compound was also produced by the action of horseradish peroxidase on DCPD in vitro. Six fungi sensitive to DCNA were grown on potato-dextrose agar containing 10 gg/ml of DCNA, DCPD, or ADCAA. DCPD and ADCAA did not significantly affect the growth of any of the fungi tested as compared with controls whereas DCNA completely inhibited or reduced the growth rate in all cases.Because 2,6-dichloro-4-nitroaniline (DCNA) is widely used for control of plant disease, knowledge of its fate in soil is important for its safe use as a fungicide. Experiments on its persistence in soil have revealed that breakdown, apparently as a result of microbial action, is more rapid in soil previously treated with DCNA (Groves and Chough, 1970). In the latter case, [14C]DCNA added to soil was utilized rapidly and 25 to 50% of the radioactivity associated with the chemical was recovered in CO2 evolved from the treated soil. When [14C]DCNA was added to soils not pretreated with DCNA, no 14C02 was evolved. However, it was not determined if DCNA had been altered without evolution of 14C02. Wang and Broadbent (1973) reported that only 2-4% of added DCNA was recovered after 10 days from glucose, alfalfa, and rice straw amended flooded soils as compared with 83.5% recovery from unamended flooded soils. From unamended upland soil, they reported that 99.5% of the DCNA was recovered unchanged after 4 weeks. In all the early studies, metabolic products of DCNA other than CO2 were not identified and potential toxicity of the metabolites was not studied.