The fluorescence derivatization of nucleotides with 2-(5-chlorocarbonyl-2-oxazolyl)5, 6-methylenedioxybenzo-furan in the presence of sodium azide and the separation of the derivatives by high-performance liquid chromatography are described. The reagent reacts with 5'-terminal hydroxyl groups of nucleotides to produce the correspoding fluorescent carbamates. The derivatives of mono- and oligonucleotides are separated by chromatography on a reversed phase column (TSKgel ODS-80TM) and the derivatices of octa- and deca-nucletides on a size exclusion column (TSKgel G3000SWXL). The detection limits (signal-to-noise ratio-3) are 0.8-6.0 pmol on column. 5'-Phosphorylated nucleotide also gives a fluorescent derivative after alkaline phosphatase-mediated dephosphorylation.