A process for isolating nucleic acid from a nucleic acid-containing sample, which comprises: (a) providing a chaotrope; (b) providing a nucleic acid binding solid phase capable of binding nucleic acid in the presence of the chaotrope; (c) providing a source of NH4+ or NH3; (d) contacting the sample with the nucleic acid binding solid phase in the presence of a liquid phase comprising the chaotrope and the NH4+ or NH3; and (e) optionally separating the solid phase with the nucleic acid bound thereto from the liquid phase.