Chlorobenzilate (ethyl 4,4′-dichlorobenzilate), chloropropylate (isopropyl 4,4′-dichlorobenzilate), and bromopropylate (isopropyl 4,4′-dibromobenzilate) were metabolized by rat liver preparations, with the microsomal and the nuclear supernatant fractions being most active. The limiting reaction was cleavage of the ester linkage by carboxylesterases, which showed greater activity for the ethyl ester (chlorobenzilate) than for the isopropyl ester (chloropropylate and bromopropylate). This initial reaction was blocked by the organophosphate DFP (diisopropyl phosphorofluoridate). SKF-525A enhanced to some extent the degradation of chlorobenzilate by the mitochondrial and possibly the microsomal fractions. p-Chlorobenzoic acid from chlorobenzilate and chloropropylate and p-bromobenzoic acid from bromopropylate were the identified end products of acaricide metabolism by the hepatic enzymes.