To compare the efficacy and adverse reactions of terazosin and alfuzosin in treatment of acute urinary retention in patients with benign prostatic hypertrophy. Design: Case control study. Setting: Emergency department of a regional hospital in Hong Kong. Methods: Our study included all adult male with age at least 18 years old presented with acute urinary retention, having residual urine volume greater than or equal to 300 ml after urinary catheterisation and with a presumed diagnosis of benign prostatic hypertrophy. Patients treated with terazosin from December 2013 to February 2014 were retrospectively included while patients treated with alfuzosin from April to September 2014 were prospectively included. We compared the two groups on: trial without catheter (TWOC) rate, potential adverse effects including drug-associated postural hypotension, haemodynamic changes and prolongation of corrected QT interval in electrocardiogram. Cost effectiveness analysis was performed. Results: A total of 116 patients were included with 59 and 57 patients in the terazosin and alfuzosin group respectively. Logistic regression showed that residual urine volume (odds ratio [OR]=0.998, 95% confidence interval [CI]=0.996-0.999, p=0.008) and presence of precipitating factors (OR=2.264, 95% CI=1.045-5.793, p=0.045) were independent predictors of successful TWOC. There was no significant difference in the TWOC rate for patients treated with alfuzosin and terazosin. There was significantly more symptomatic postural hypotension in the terazosin group compared with the alfuzosin group. The number need to treat with alfuzosin for terazosin to avoid one adverse drug effect was 12.3 patients (95% CI=4.7-21.6) and 9.9 patients (95% CI=5.3-84.6) to reduce one postural hypotension and symptomatic postural hypotension respectively. Conclusions: Alfuzosin is comparable to terazosin in TWOC rate. However, alfuzosin is associated with a lower rate of symptomatic postural hypotension and less haemodynamic impact than terazosin.