Trace levels of oxytetracylcine spiked into commercial milk samples are extracted, cleaned up, and preconcentrated using a C[subscript 18] solid-phase extraction column. The extract is then analyzed by a high-performance liquid chromatography (HPLC) instrument equipped with a UV detector and a C[subscript 18] column (150 mm x 4.6 mm x 3.5 [mu]m). An isocratic mobile phase of 0.010 M oxalic acid/acetonitrile/methanol (in 15/2/2 ratio by volume) is employed with an average elution time of 5 min. The method has been successfully used in an upper-class instrumental analysis laboratory course to determine the concentration of oxytetracycline at 50 [mu]g/g in the spiked milk sample. Students' results show an RSD of 18% and a percent error of -1%. (Contains 5 figures and 2 tables.)