A series of 4-aminomethyl-2, 3, 4, 9-tetrahydrothiopyrano [2, 3-b] indole derivatives was synthesized and evaluated for analgesic activity. Preliminary structure-activity relationship analysis showed that substitution on the benzene portion of the indole ring reduced the analgesic activity, whereas a short-chain N^b-alkyl substituent enhanced the potency, as exemplified by an N^b-methyl substituted analogue. This compound was equipotent to morphine in the acetic acid writhing assay using mice.