A data storage medium is disclosed comprising a solid support matrix including an optional stabilising reagent or reagents in a dry form, for use as a support for artificially synthesised oligonucleotide sequences encoded with data. Preferably the matrix is fibrous (for example cellulose, or glass, fibres) formed into a support of sufficient strength to hold the oligonucleotide sequences. The stabilising reagents are preferably a combination of a weak base, and a chelating agent, optionally, uric acid or a urate salt, and optionally an anionic surfactant.