The quinoxaline-1,4-dioxide compound carbadox is used in pigs as a growth-promoting agent for the improvement of weight gain and feed efficiency. It is also administered as an antibacterial drug against dysentry and bacterial enteritis in pigs. Following oral administration it metabolises to the compound Quinoxaline Carboxylic Acid (QCA) (3). Maximum residue levels were established for 30 ppb in liver and 5 ppb in muscle however it was concluded that use of carbadox according to good practice in veterinary medicine does not represent a dietary hazard to human health.