A procedure has been developed for determining buquinolate (ethyl 4-hydroxy- 6,7- diisobutoxy - 3 - quinolinecarboxylate) in finished chicken feeds. In the procedure, a chloroform extract of the feed is concentrated to a small known volume, separated from background substances by thin layer chromatography on silica gel (two solvent systems), eluted from the plate, and compared fluorometrically with reference standard buquinolate. No background interference was found from 157 feed samples investigated or from 11 common feed additives. Recovery experiments on 31 samples at levels ranging from 0.0044 to 0.0143% buquinolate averaged 99.7% with a standard deviation of 3.3. The method is equally applicable to both fresh and aged feeds. This method was studied collaboratively, results were good, and the method is recommended for adoption as official, first action