Several unknown halogenated compounds were detected in Niagara River fish using a method similar to the AOAC multiresidue method for chlorinated pesticides in high-moisture foods. From gas-liquid chromatographic-mass spectrometric (GLC/MS) data and GLC retention times on 3 columns, 7 of the compounds were identified as 4-chloro-α,α,α-trifluorotoluene (0.17—2.0 ppm), 2-chloro-α,α,α-trifluorotoluene (0.002—0.1 ppm), 3,4-dichloro-α,α,α-trifluorotoluene (0.02—0.28 ppm), 2,4-dichloro-α,α,α-trifluorotoluene (0.02—0.17 ppm), 2,3-dichloroa, α,α,α-trifluorotoluene (trace-0.005 ppm), 2,6-dichlorotoluene (not quantitated), and 2,4,5-trichlorotoluene (0.31 ppm was found in the only sample quantitated). Other isomers of triand tetrachloro-α,α,α-trifluorotoluene and di-, tri-, and tetrachlorotoluene were also present in these samples. Recoveries of the specific chlorinated trifluorotoluenes identified in these samples ranged from 86 to 108%.