The book "Determination of Sulfadiazine and Trimethoprim in Farmed Fish by LC/MS" offers a comprehensive study on the determination of sulfadiazine and trimethoprim in farmed fish, particularly in the muscle and skin of sea bream (Sparus aurata). The study describes the conditions under which the fish were kept in seawater, as well as the administration of medicated feed over a period of five days. The authors have developed and validated a method for extracting residues from fish tissue that meets the requirements of the European Directive 2002/657/EC. The use of liquid chromatography-mass spectrometry (LC/MS) allows for the precise determination of the analytes. The results of this investigation are of great importance to protect consumers from unwanted residues in fish products and to ensure compliance with established maximum limits.