1,1-Dichloro-2,2-bis(4-chlorophenyl)ethane(DDE) has been used to study the ability ofPseudomonas acidovoransM3GY to transform DDE and its unchlorinated analog, 1,1-diphenylethylene (DPE).It has been used to investigate the role of incubation time, solvent type, yeast inoculum growth stage and concentration on the results of yeast assay for estrogenic compounds.