Prazosin HCl was administered in dosages of 1.5–4.5 mg/day for 4 weeks to 40 patients suffering from dysuria accompanying prostatic hyperplasia. Significant reductions were observed in the mean frequency of night-time and 24-hour urination. Additionally, significant improvements were recorded for the time for start of urination, time from start to finish of urination and related variables. The improvements correlated with dosage levels. Objective variables measured by urine flow rates also exhibited significant improvement. A statistically significant decrease in systolic without a decline in diastolic blood pressure was observed. Slight dizziness was observed in 1 patient and elevated laboratory test values in another, but neither warranted discontinuation of the medication; however, 1 patient did have two doses of medication held. Overall, the drug was judged benefical to some degree in 95% of the patient