Bladder cancer(BC)is the second urological malignancy in incidence,currently being one of the most neoplasms studied with profile and biology poorly defined.In the world,BC is responsible by about 386000 new cases and 150000 deaths annually with considerable economic impact and high costs for health systems.After its discovery more than 20 years,micro RNAs(miRNAs)have been recognized as molecules that work specifically in post-transcriptional control in majority of eukaryote genomes.MiRNAs are a family of small noncoding RNAs of 19-25 nucleotides in length,expressed in a wide variety of organisms,comprising plants,worms and mammals,including humans.They have a fundamental role in physiological and pathological processes in organs and tissues in a context-dependent manner.This review brings new roles of protective and oncogenic miRNAs linked to carcinogenesis of urothelial carcinoma of the bladder,and associated with behavior of disease.Many studies have demonstrated promising roles of miRNAs working as diagnostic and prognostic biomarkers or involved in target therapies,consolidating miRNAs as crucial players in human cancer.This review allowed a reflection about the true functions of miRNAs in bladder carcinogenesis.Not only by their wide capacities of action,but also by abilities in define the cell date.The future of anti-tumor target therapies will be based not in one,but in groups of miRNAs working together in several steps of carcinogenic process,being able to identify the disease,predicting behavior and effectively treat bladder cancer.