The selective sea lamprey (Petromyzon marinus) larvicide 3-trifluoromethyl-4-nitrophenol (TFM) is currently used to control parasitic sea lampreys in tributaries to the Great Lakes basin. The concentration and persistence of TFM and its major metabolite, TFM glucuronide (TFM-glu), was determined in fillet tissue of fish after a typical stream application. Rainbow trout (Oncorhynchus mykiss) and channel catfish (Ictalurus punctatus) were exposed to a nominal concentration of 12.6 nmol/mL TFM for about 12 h during a sea lamprey control treatment of the Ford River in Michigan. Concentrations of TFM and TFM-glu were greatest in the fillet tissues during the exposure period, with greater residues in channel catfish (wet wt; mean, 6.95 nmol/g TFM; mean, 2.40 nmol/g TFM-glu) than in rainbow trout (wet wt; mean, 1.45 nmol/g TFM; mean, 0.93 nmol/g TFM-glu). After the exposure period, residues in both species decreased by 90-99% within 6-12 h and were less than the quantitation limit (<0.03 nmol/g) within 36 h.