Residue methods were developed for the determination o f the coccidiostat robenidine in egg, the benzimidazoles (13) in liver (albendazole 2-amino albendazole sulphone, albendazole sulphoxide, albendazole sulphone, thiabendazole, oxfendazole or fenbendazole sulphoxide, hydroxy mebendazole, amino flubendazole, fenbendazole sulphone, oxibendazole, mebendazole, flubendazole and albendazole) and the triphenylmethane dyes (4) in salmon (malachite green, crystal violet, leucomalachite green and leucocrystal violet). The methods were validated according to the criteria defined in Commission Decision 2002/657/EC. Robenidine was extracted from egg with acetonitrile and the sample extracts analysed by liquid chromatography (LC) with ultraviolet (UV) spectrophotometric detection at 317 nm. The decision limit (CCa) and the detection capability (CCP) were 10 |xg.kg_I and 17 ng.kg'1 respectively. The benzimidazoles were extracted from liver samples with ethyl acetate, sample extracts were defatted with hexane and cleaned up by automated solid-phase extraction (SPE) on Ci8 cartridges. Aliquots o f the extracts were analysed by LC with UV detection at 298 nm. The CCa values ranged between maximum residue limit (MRL) + 12% and MRL + 25% and the CCP ranged between MRL + 25% and MRL + 45%. The triphenylmethane dyes were extracted from salmon with acetonitrile and pH 3 buffer, extracts were cleaned up using cation-exchange SPE on sulphonic acid (SCX) cartridges and the sample extracts were analysed by liquid chromatography tandem mass spectroscopy (LC-MS/MS). CCa for malachite green, leucomalachite green, crystal violet and leucocrystal violet were 0.17, 0.15, 0.40 and 0.17 iig-kg'1 respectively and CCP were 0.30, 0.35, 0.80 and 0.32 ng.kg 1 respectively. All research undertaken in this thesis was published in peer reviewed journals. This work has made a significant contribution to residues science as more novel methods have become available for surveillance of these drugs at national and international level. The methods developed in this research also provide a legal basis for prosecuting individuals who use these veterinary products without adhering to EU legislation. Ultimately the work enhances food safety as methods developed help to eliminate the hazards associated with drug residues entering the food chain.