A sensitive and selective analytical method utilising liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-ESI-MS/MS) operated in multiple reaction monitoring mode was developed for the semi-quantitative determination of 19 biogenic amines and amino acids in mammalian (porcine) decomposition fluid. The effect of the matrix on analyte response was initially investigated by diluting crude samples and by injecting various volumes in the LC-MS system. It was found that the matrix had little effect on analyte signal intensities when small volumes (0.1 to 1 μL) of crude samples or 1:10 diluted samples were injected into the LC-ESI-MS/MS system. The standard addition method was also investigated for quantitative assessment but proved unsuccessful, possibly due to poor ionisation of the electrospray interface at high analyte concentrations. Therefore a method using external calibration was used for semi-quantitative determination of the analytes in decomposition fluid. The LC-ESI-MS/MS method enabled identification of all target compounds as being present. In addition a 14-day cyclic trend in the concentrations of two amino acids, phenylalanine and tryptophan, was tentatively established. General increasing trends with respect to time and temperature were also observed for putrescine and indole.