The aim of this study was to determine the effects of boiling on nitrofuran 3-amino-2-oxazolidinone (AOZ) residues in eggs. The use of furazolidone in food-producing animals is banned within the EU and Turkey. The nitrofuran AOZ residues in raw and boiled eggs were analysed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a chromotographic run of 20 min. The method validation was done according to the criteria laid down in Commission Decision No. 2002/657 EC. Linearity was proved between 0 to 1.5 mu g/kg, decision limit (CC alpha) was 0.70 mu g/kg, detection capability (CC beta) was 0.77 mu g/kg, recovery values ranged between 88-97.9% and repeatability (CV) was 3-4.3%. The detected avarage nitrofuran AOZ residue level in 13 uncooked eggs by LC-MS/MS was 0.86 +/- 0.017 mu g/kg which was increased to 2.42 +/- 0.037 mu g/kg after boiling. In this study, it was surprisingly found that protein-bound side-chain metabolite, nitrofuran AOZ levels in eggs were significantly increased after boiling. This finding runs counter to the claim that heat process in general should decrease various antibiotic levels in food. The observed increase (P<0.001) in nitrofuran AOZ levels in boiled eggs relative to uncooked eggs may be due to enhanced efficiency of extraction in boiled samples. Therefore boiled eggs should be used for analysis of nitrofuran AOZ levels in order to obtain more reliable and more predictive results.