Novel derivatives of natural muscarine and allo-muscarine, i.e. the benzyl ethers (-)-10 and (-)-12 and the benzoate (-)-13, were synthesized in very high enantiomeric excess. Target compounds were tested in vitro on guinea pig tissues, and their muscarinic potency was evaluated at M2 (heart force and rate) and M3 (ileum and bladder) receptor subtypes. The derivatives under study were also assayed in vivo on pithed rat. In addition, muscarinic receptor heterogeneity was investigated by determining the affinity and the relative efficacy of compounds (-)-10, (-)-12 and (-)-13 at M2 (heart force and rate) and M3 (ileum and bladder) receptor subtypes.