Isothiazole (8a, b), isoxazole (14) and thiophene (19a,b) analogues of the potent, M1 selective muscarinic agonist, hexyloxy-TZTP, lb, were synthesized and tested in vitro for muscarinic receptor affinity and M1 efficacy. All the analogues had lower affinity and efficacy at the M1 muscarinic receptors than lb.