This book deals with the synthesis, characterization and application of quinazolinone based reactive dyes by conventional method and applied on fibres like silk, wool and cotton. It also reported good quality of introduction and literature review of reactive dyes as well as quinazolinone based reactive dyes. A detailed study of in vitro Pharmacological screening (antibacterial and antifungal), Fastness properties, Colorimetric data (L_, a_, b_, c_, H_, K/S) and Thermogravimetric analysis (TGA) were also investigated. These dyes showed generally moderate to very good light fastness and good to excellent washing and rubbing fastness properties and also showed good antimicrobial activity as well as good thermal stability.