Nocturia is a common symptom associated with benign prostatic hyperplasia which can persist even after effective treatment of BPH. Other causes may be responsible. We investigated a group of patients who were treated for BPH and continue to have nocturia. Our study has found a high prevalence (85.4%) of nocturnal polyuria in this group of patients. It has important clinical implication since the condition can be effectively treated with oral desmopressin. Empirical treatment without a routine frequency volume chart may be appropriate due to its high prevalence.