Eprinomectin, moxidectin, abamectin, doramectin, and ivermectin are drugs used to control parasitic infections in both meat-producing and nonmeat-producing animals. A number of analytical methods are available to analyze these anthelmintic drugs individually. A multiresidue screening method was developed for these drugs; however, the initial attempt to derivatize eprinomectin following the method published by Merck scientists was unsuccessful because the eprinomectin derivatization reaction was temperature- and time-dependent. The optimum time and temperature for the completion of eprinomectin derivatization were 90 min and 65 degrees C, respectively, without appreciable effect on the remaining 4 drugs. Beef liver samples were fortified with 0, 25, 50, and 100 ppb mixed standards of eprinomectin, moxidectin, abamectin, doramectin, and ivermectin. Each set of 4 levels of recoveries was repeated 10 times with all 5 compounds. The average of 10 recoveries of 5 compounds at all 4 levels of fortification was > 70%; the coefficient of variation was < 20%.