The goals of this study are evaluation the effect of intravenous (IV) granisetron on the duration of sensory and motor block produced by intrathecal hyperbaric bupivacaine and also post-operative nausea and vomiting in patients undergoing outpatient cystoscopy. 62 patients, undergoing cystoscopy received either 3 mg IV granisetron or placebo 15 minutes before the spinal block. Sensory and motor block were assessed after the intrathecal injection of bupivacaine every 2 minutes until the maximum block was achieved and thereafter every 15 minutes until recovery from the sensory and motor block. Demographic data were not statistically different in the study groups. Duration of sensory and motor block were also not statistically different between the study groups (P = 0.060 and P = 0.070 respectively). No patient in either group had vomiting. Seven patients in saline and zero patient in granisetron group had nausea that was statistically significant (P = 0.040). Time to discharge after surgery was 243 ± 21 and 239 ± 24 minutes in granisetron and control group respectively (P = 0.150). Systemic granisetron had no effect on the duration of sensory and motor block produced by spinal anesthesia with hyperbaric bupivacaine.