Paruresis, characterized by the difficulty or inability to urinate in a variety of social contexts, is a scientifically under-studied phenomenon. One reason for this state of affairs is the paucity of reliable and valid measures for assessing this problem. The present article attempted to address this limitation by investigating the psychometric properties and validity of a new measure of paruresis: the Shy Bladder Scale (SBS). In two undergraduate samples, the SBS demonstrated excellent internal consistency and a stable factor structure assessing difficulty urinating in public, impairment and distress, and paruresis-related fear of negative evaluation. Undergraduate students evidenced very low levels of paruresis-related concerns. In contrast, SBS scores were markedly elevated among individuals recruited from an online support network who appeared to meet diagnostic criteria for paruresis-specific social phobia. Our findings highlight the SBS's potential utility as a measure of paruresis in clinical and research contexts.