An improved LC-MS/MS method for the determination of semicarbazide in whole egg is described. Waters OASIS-MCX cation exchange purification cartridges increased the sensitivity for analysis by LC-MS/MS. The validation study was carried out according to criteria and requirements of Commission Decision 2002/657/EC for confirmatory analysis and provided the data as follows: The correlation coefficient for the matrix calibration curve, in the range of 0-5 microg kg(-1), was r=0.9968. The detection capability and decision limit, measured according to ISO11843-2, were CCalpha=0.20 microg kg(-1) and CCbeta=0.25 microg kg(-1). Repeatability (CVSr) and within-laboratory reproducibility (CVSwr) determined for the concentration levels of 0.2, 0.5 and 1.0 microg kg(-1) SEM ranged from 11.9 to 5.7% and 11.8 to 6.3%, respectively. The validated method was applied to investigate SEM stability in incurred materials (egg homogenates) during long-term storage at -20 degrees C and 4 degrees C. The study proved by a two-sampling test that SEM at levels of 17. 7, 1.2, 10.6 and 0.47 microg kg(-1) was stable for up to 12 months.