A practical resource for everyone involved in the gene therapy field and in the design of effective gene delivery systems, this volume presents an overview and update of recent advances in the field of non-viral methods for the in vivo transfer of therapeutic genes to biological targets using conventional routes of administration. Methods to control the spatial and temporal modulation of gene function in vivo as well as the level, duration, specificity, and fidelity of gene expression are described. The rational design and the applications of a variety of non-viral gene delivery systems, such as cationic lipid-, polymer-, and (poly) peptide-based systems, are exemplified for the control of location of therapeutic genes administered by various routes. Current and potential clinical applications of gene-based medicines are presented for the prevention, correction or modulation of diseases. Examples of current applications of plasmid-based systems for genetic vaccination, treatment of genetic disorders such as cystic fibrosis, and treatment of acquired diseases such as cancer are also provided.