​This book presents drug repurposing strategies to combat infectious diseases and cancer. It discusses key experimental and in silico approaches for modern drug repositioning, including signature matching, molecular docking, genome-wide associated studies, and network-based approaches aided by artificial intelligence. Further, the book presents various computational and experimental strategies for better understanding disease mechanisms and identify repurposed drug candidates for personalized pharmacotherapy. It also explores the databases for drug repositioning, summarizes the approaches taken for drug repositioning, and highlights and compares their characteristics and challenges. Towards the end, the book discusses challenges and limitations encountered in computational drug repositioning.