As intracellular RNA levels are determined by the balance between RNA synthesis and decay, RNA stability is a critical factor in the quantity of intracellular RNA. Recent advances in epitranscriptomic measuring techniques have shown that RNA modifications, such as methylation and acetylation, affect RNA stability, including those of messenger RNA (mRNA) and noncoding RNA (ncRNA) such as transfer RNA (tRNA) and ribosomal RNA (rRNA). In addition, some viruses infected into cells avoid innate immunogenicity through the RIG-I signaling pathway by modifying their genomic RNAs. In this chapter, we focus on epitranscriptomic regulation for RNA stability. These epitranscriptomic regulations of RNA stability have also been utilized in commercial applications, such as development of gene therapy agents. This chapter also addresses biotechnological applications of RNA stabilization that use modified nucleosides and measurement technologies that evaluate RNA stability.