Abstract: The present invention relates to therapeutically active azacyclic or azabicyclic compounds of formula I ##STR1## and to pharmaceutical formulations comprising these compounds and methods of treatment comprising administering these compounds to a subject in need of treatment. The novel oxadiazole compounds, such as (.+-.)-3-butyloxy-4-(1-azabicyclo[2.2.2]octyl-3-oxy)-1,2,5-oxadiazole, are useful in treating central nervous system disorders caused by malfunctioning of the muscarinic cholinergic system.