Despite its toxicity, in low concentrations nitric oxide (NO) is one of the smallest endogenous molecules with a particularly important role in the regulation of several biochemical pathways of the human body. The potential of L-Histidine modified clays (organoclays) for storage and therapeutic release of nitric oxide was assessed. Materials were characterized by powder X-ray diffraction, TG-DSC, IR spectroscopy, nitrogen adsorption at -196 °C. The NO storage and release kinetics was studied both in gas and liquid phases. For some materials an improvement on both, the released amounts and the release profile, was obtained for the organoclays in relation to the respective raw clays. Assays with HeLa cells indicated that the materials have low cytotoxicity.