The effect of sodium hypochlorite (NaClO) on nucleic acids (NAs) was investigated. The effect of biomolecular structure on resistance to hypochlorite was analysed: Plasmid bacterial DNA, calf thymus DNA, synthetic polyadenylic-uridic acid samples were studied, as well as individual nucleotides (adenosine-5'-tetraphosphoric acid and guanosin-2', 3-cyclophosphoric acid). The effect of sodium hypochlorite on DNA was investigated depending on the concentrations of the components. We have also performed detailed analysis of the kinetics of the reaction between the NAs and NaClO. It was found that both the destruction of the secondary structure of DNA (denaturation) and the chemical modification of nitrogenous bases, presumably chlorination, occur. Presence of a stable double-stranded structure of DNA slows down the chemical reaction of sodium hypochlorite with nitrogenous bases of DNA.