Molecular biology will have a profound impact upon the treatment of disease. Molecular techniques provide protein products for treatment of more diseases each year. The understanding of pathophysiology at the molecular level allows for improved drug design. Antisense technology can selectively control gene expression. Gene therapy is potentially the most important aspect of molecular biology. Physical and viral transduction mechanisms are being developed toward this end. Gene replacement, creation of antisense oligonucleotides, and prodrug strategies are being developed. Currently, gene replacement and prodrug therapy are feasible in at least a few cases, but further study will yield additional applications.