Hypotension during spinal anesthesia is a serious complication in elderly patients. We evaluated the effect of glycopyrrolate on hypotensive responses in elderly patients undergoing spinal anesthesia. Sixty-six patients older than 60 yr of age scheduled for elective surgery with spinal anesthesia were included in the study. They received either glycopyrrolate 0.2 mg (group G) or normal saline (group C) intramuscularly 15 min before spinal anesthesia. The following outcomes were evaluated after the induction of spinal anesthesia: the incidence of hypotension and bradycardia, the ephedrine requirement, mean arterial pressure, heart rate, and the incidence of nausea and vomiting. Twenty-three of 33 (70.0%) patients in group C experienced hypotension compared with nine of 33 (27.3%) patients in group G (difference = 42.7%; 95% confidence interval [CI]: 18.4 to 60.2; P = 0.001). The median [interquartile range] amount of ephedrine required was 5 [0-15] mg in group C compared with 0 [0-5] mg in group G (difference = 5.0 mg; 95% CI: 2.7 to 7.3; P = 0.001). Nine (27.3%) patients in group C experienced nausea and vomiting compared with 2 (6.1%) in group G (difference = 21.2%; 95% CI: 3.0 to 38.7; P = 0.044). Three (9.1%) patients in group C experienced bradycardia compared with 1 (3.0%) patient in group G (difference = 6.1%; 95% CI: -7.6 to 20.8; P = 0.613). Prophylactic intramuscular glycopyrrolate reduced the occurrence and severity of hypotensive responses, the requirement for ephedrine, and the incidence of nausea and vomiting in elderly patients undergoing spinal anesthesia. The trial was registered at the Clinical Research Information Service, Republic of Korea (KCT0000556).