Disorders of micturition (voiding dysfunction), the essence of urinary bladder function, are unknown to the discipline of pathology, despite their prevalence and profound socioeconomic impact. Their pathogenesis has remained largely unknown, their diagnosis often difficult or uncertain, and the outcome of their management generally unpredictable. A new approach to morphologic study of the bladder has been developed to identify microstructural correlates of its function. Application of this approach to endoscopic biopsies culminated in the concept of functional pathology of urinary bladder muscularis. The basis, elements, current status, and diagnostic potential of this new concept are presented in relation to the major forms of clinical voiding dysfunction.