Antisense RNA (asRNA) refers to a type of single-stranded RNA. It hybridizes with protein coding messenger RNA (mRNA) and complements it to inhibit its translation into a protein. Eukaryotes and prokaryotes, both have naturally occuring asRNAs in them. They can be divided into two types including short and long non-coding RNAs (ncRNAs). asRNAs primarily control the gene expression and are widely utilized as tools for gene knockdown. Antisense technology offers effective experimental methods for examining gene function and gene regulation by modifying gene expression in mammalian cells. Many RNA-based antisense therapies are being developed currently. However, effective delivery of these therapies to target tissues remains the primary barrier in their clinical application. Antisense technology has a wide range of applications in the treatment of numerous diseases such as viral infections, cancer, and immunological, cardiovascular, ocular and neurological diseases. This book contains some path-breaking studies in antisense technology. It consists of contributions made by international experts. This book is a vital tool for all researching or studying antisense RNA as it gives incredible insights into its design and delivery.