Summary— The results of cystometrograms and ice-water tests (IWTs) were retrospectively evaluated in 557 patients with overactive bladders, lower motor neuron lesions or pure stress incontinence. The IWT was considered positive when, following ice-water instillation, the fluid was expelled from the bladder within 1 min. The test was considered false negative when no fluid escaped despite a sustained detrusor contraction of the same magnitude as the micturition contraction. Ninety-seven percent of patients with complete and 91% of those with incomplete upper motor neuron lesions had a positive or a false negative IWT. About 75% of the patients with multiple sclerosis, Parkinson's disease or previous cerebrovascular accident had a positive IWT. All patients with lower motor neuron lesions or pure stress incontinence had a negative IWT. There was a significant correlation between a positive IWT and an abnormal sensation of bladder filling and inability to inhibit micturition voluntarily, as well as between a negative IWT and the occurrence of phasic detrusor contractions during cystometry. The study shows that the IWT is a sensitive test for differentiating upper from lower motor neuron lesions. It is also a useful parameter for functional subdivision of overactive bladders. In patients with voiding dysfunction in the absence of lower urinary tract inflammation, a positive test is an indicator of a silent or overt neurological disorder.