Post-mortem biochemistry of serum markers has been the subject of numerous studies, but in-situ marker stability after death has not been sufficiently evaluated yet. Such laboratory analyses are especially necessary in the cases of functional deaths without morphological evidence of the death causes and also in cardiac death cases with only very short survival times. The aim of the study was to determine the post-mortem stability of commonly-used serum markers at predefined time points. In 20 cases, peripheral venous samples were taken starting immediately after circulatory arrest and ending 48 hours after death. Serum creatinine, urea, 3-β-hydroxybutyrate, tryptase, myoglobin, troponin T, creatin kinase and creatin kinase-MB have been included. For all markers, we observed increasing marker levels for longer post-mortem intervals. Significant marker level changes began two hours after death. Excessive increases were observed for cardiac and muscle markers. Marker levels showed high intra-assay precision. Furthermore, the markers were robust enough to withstand freeze-thaw cycles. Potential contamination of arteriovenous blood did not influence the post-mortem marker levels. Post-mortem blood should be sampled as soon as possible, as increased post-mortem intervals may heavily change marker levels in-situ in individual cases, whereas the markers are mostly unaffected by laboratory conditions.