In the course of investigations of structure and conformation-activity relationships of cyclic acetylcholine analogues, both the enantiomers of trans-3-acetoxy-1-methylthioniacyclohexane were prepared. These two esters and the corresponding racemate of the cis-ester were tested for nicotine- and muscarine-like activity. The stereoisomeric cyclic analogues differ substantially in pharmacological activity. The cis-sulfonium ester shows the highest nicotinic potency (1/25 the nicotinic potency of acetylcholine), and the (+)-trans-ester has no agonistic properties when tested at nicotinic receptors, but it shows the highest muscarinic potency in this series.