Bladder cancer is the most common malignancy of the urinary tract and one of the most prevalent cancers worldwide. The bladder microbiota is strongly associated with different statuses of bladder cancer. The increased abundance of microbes such as Schistosoma, Pseudomonas, Streptococcus, Mycobacterium, Bacteroidetes, and Klebsiella is associated with the development of bladder cancer during tumorigenesis. Improved understanding of age-related alterations to the immune system and gut and urinary microbiomes could provide possible insights into bladder cancer development and progression in the elderly. Mitochondrial DNA (mtDNA) content has been shown to be associated with cancer susceptibility. Patients diagnosed with bladder cancer have significantly decreased mtDNA. Cancer prevention strategies are theoretically appealing although often difficult to implement, owing to the multifactorial pathogenesis of most cancers. This book focuses on the diagnosis and prevention of bladder cancer.