The present invention is directed towards a method of regulating smooth muscle tone, comprising the introduction, into smooth muscle cells of a subject, of a DNA sequence encoding a protein involved in the regulation of smooth muscle tone, and expression of the DNA sequence in a sufficient number of smooth muscle cells of the subject to regulate smooth muscle tone in the subject. Specifically, the invention provides methods of gene therapy for treating erectile dysfunction, bladder dysfunction, and other smooth muscle disorders. The present invention also provides recombinant viral and non-viral vectors comprising DNA encoding a protein involved in the regulation of smooth muscle tone. Further provided by the present invention is a smooth muscle cell which expresses a gene encoding a protein involved in the regulation of smooth muscle tone.