OBJECTIVES: To evaluate predictors of the response to doxazosin, a selective alpha-adrenoceptor antagonist, when used for the treatment of lower urinary tract symptoms in men with Parkinson's disease. METHODS: In a prospective study, 33 consecutive men (mean age 59.2±7.0 years) with Parkinson's disease and lower urinary tract symptoms were evaluated. Neurological dysfunction was assessed with the Unified Parkinson's Disease Rating Scale. Urological assessment was performed at baseline and after 12 weeks of treatment with 4 mg/day of extended-release doxazosin, including symptom evaluation with the International Continence Society male short-form questionnaire, an assessment of the impact of lower urinary tract symptoms on quality of life and urodynamics. Clinical and urodynamic predictors of response were specifically evaluated. RESULTS: Compared with the score at baseline, the total International Continence Society male short-form score was reduced after doxazosin administration, from 17.4±7.5 to 11.1±6.9 (p<0.001). The impact of lower urinary tract symptoms on quality of life was also significantly reduced, from 1.8±1.1 to 1.0±1.0 (p<0.001) and the maximum urinary flow varied from 9.3±4.4 to 11.2±4.6 ml/s (p = 0.025). The severity of neurological impairment was the only predictor of the clinical response. Additionally, patients with a Unified Parkinson's Disease Rating Scale score lower than 70 had a significantly higher chance of clinical improvement with doxazosin treatment than those with higher Unified Parkinson's Disease Rating Scale scores did (RR = 3.10, 95% CI = [1.15 to 5.37], p = 0.011). CONCLUSIONS: Doxazosin resulted in the improvement of lower urinary tract symptoms and the maximum flow rate and was well tolerated in men with Parkinson's disease. The response to treatment is dependent on the severity of neurological disability.