INTRODUCTION: Each analyte has its own stability and storage conditions if analysis could not be done immediately. It's important to take care of optimal storage conditions in order to keep constant concetration of the analyte for longer period. This research describes storage possibilities of samples that are used for determination of neuron specific enolase which is considered as unstable analyte. Neuron specific enolase (NSE) is a recognized biomarker for assesment of neurological outcome in different neurological diseases. It has important role in many tumors. METHODS: Ten blood samples for NSE testing were chosen for this research. Samples were centrifuged after the coagulation process. Every sample was divided into three portions. NSE is determined from one portion with ECLIA method and the other two portions were stored. The sample which was analysed for NSE concentration first after the blood sampling was control sample. The other sample was put on the temperature -20 ˚C and the third was frozen on temperature -80 ˚C. Samples were stored for a month in the laboratory, and then reanalysed. After that, a comparison was made between results of control samples and of those that were stored with Wilcoxon's statistical test. OBJECTIVES: The aim of this study was to investigate the effect of different storage condition on NSE stability in serum as well as to find out which storage condition could be recommended for NSE analysis in serum. RESULTS: Concetration of NSE in samples that were stored on temperature -20 ˚C showed significantly different results from the control samples, while the NSE concentrations of the samples that were stored on temperature -80˚C did not show the difference. CONCLUSION: The temperature -80 ˚C is recommended for storage of serum samples for NSE assaying because that storage option shows lower variability in test results than storage on -20 ˚C. KEYWORDS: Biomarkers, storage, neuron specific enolase, NSE, ECLIA.