What's known on the subject? and What does the study add? In our everyday practice as urologists, we often face diagnostic uncertainty that prompts us to perform a range of diagnostic tests to determine the probability that a patient has an underlying condition. Unfortunately, some diagnostic tests do not help us 'rule in' our 'rule out' a disease. These clinically unhelpful tests are not the best allocation of our healthcare system's resources. This series will discuss the quality of evidence supporting the use of common diagnostic tests in urology. This discussion represents an important dimension of the decision-making process and appropriate interpretation of these tests. Through this series we hope to improve patient care by encouraging and informing readers to exercise selective application of these diagnostic tests to reduce the burden of rising and ultimately unsustainable healthcare costs.