To determine whether the use of intraprostatic epinephrine during transurethral resection of the prostate reduces intraoperative blood loss. A random, double-blind, prospective study was carried out on twenty-three patients that underwent transurethral resection of the prostate. Patients were divided into two groups: (1) group receiving intraoperative intraprostatic injection of epinephrine (thirteen patients) and (2) group receiving intraoperative intraprostatic injection of saline solution as placebo (ten patients). Blood loss was quantified with the following formula: irrigation solution hemoglobin × 1000/intraoperative presurgical serum hemoglobin. The variables analyzed were blood loss, resection time, presurgical prostate volume, and grams of resected tissue. Student´s t test and Pearson correlation were used for their analysis. There were thirteen patients in the epinephrine group and ten patients in the placebo group. Mean blood loss in the epinephrine group was significantly lower than in the placebo group (127.48 mL ± 77.0 mL vs. 336.63 ± 185.6 mL, 95% CI, 45-234, P < 0.001). There were no statistically significant differences in mean resected grams or mean resection time between the two groups. One patient in the epinephrine group presented with intraoperative hypertensive crisis (7.7%). Intraprostatic epinephrine injection can be used to reduce blood loss during transurethral resection of the prostate in selected patients. Cardiovascular monitoring should be carried out during its application. Resection time and grams of resected tissue continue to be the most influential factors in relation to blood loss in patients undergoing this treatment modality.