In the present study, we investigated the role of 5-hydroxytryptamine type 3 (5-HT(3)) receptors in hypnosis and analgesia induced by emulsified sevoflurane. A mouse model of hypnosis and analgesia was established by an intraperitoneal or subcutaneous injection of emulsified sevoflurane.We intracerebroventricularly (i.c.v.) or intrathecally (i.t.) administered YM-31636, a 5-HT(3) receptor agonist, to mice and observed sleep time during hypnosis. In addition, the tail withdrawal latency was measured using the tail withdrawal test, and the writhing time was determined using the acetic acid writhing test. In the hypnosis test, YM-31636 (5, 10 and 15 μg, i.c.v.) treatment significantly decreased emulsified sevoflurane-induced mouse sleep time (p < 0.05 or p < 0.01). YM-31636 (2.5, 5 and 10 μg, i.t.) treatment significantly and dose-dependently decreased the tail withdrawal latency (p < 0.05 or p < 0.01) and increased the writhing time (p < 0.01) of mice treated with emulsified sevoflurane. These results suggest that 5-HT(3) receptors may modulate the hypnotic and analgesic effects induced by emulsified sevoflurane.