In the last ten years the peroxydisulfate (PDS) application as oxidant for in-situ chemical oxidation (ISCO) technology became popular for remediation of contaminated soil and groundwater. Due to its high oxidation potential, PDS has a high capacity to degrade a wide variety of contaminants. However, due to its low use, a lot of information are not available about stability, persistence, and transport. The objective of this study was to identify the stability of unactivated PDS in presence of two soils from Czech Republic and a sea sand. Degradation rate coefficients and half-life were analyzed and the dependence on total organic carbon (TOC) and inorganic elements content, such as Fe and Mn, was studied.