Abstract: The present invention is directed towards gene therapy for erectile dysfunction through delivery and expression of a recombinant vector containing a DNA sequence encoding a protein involved in the regulation of smooth muscle tone into a smooth muscle cell. Also provided by the present invention is a method of inducing penile erection in a subject comprising the introduction and expression of a DNA sequence encoding a protein involved in the regulation of smooth muscle tone into a sufficient number of cells of the subject to induce penile erection in the subject. The present invention also provides a recombinant vector comprising the DNA of or corresponding to at least a portion of the genome of a virus, which portion is capable of directing the expression of a DNA sequence, and DNA encoding a protein involved in the regulation of smooth muscle tone operably linked to the viral DNA and capable of being expressed as a functional gene product in the target cell.