There is provided a calcium receptor modulator comprising a compound of the formula (I): ##STR00001## wherein ring A is an optionally substituted 5- to 7-membered ring; ring B is an optionally substituted 5- to 7-membered heterocyclic ring; X.sup.1 is CR.sup.1, CR.sup.1R.sup.2, N or NR.sup.13; X.sup.2 is N or NR.sup.3; Y is C, CR.sup.4 or N, Z is CR.sup.5, CR.sup.5R.sup.6, N or NR.sup.7; Ar is an optionally substituted cyclic group; R is H, an optionally substituted hydrocarbon group, etc.; and is a single bond or a double bond; R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, R.sup.7 and R.sup.13 are independently H, an optionally substituted hydrocarbon group; or a salt thereof or a prodrug thereof. Compounds of the formula (II) and (III): ##STR00002## wherein ring A is an optionally substituted 5- to 7-membered ring; Q is C, CR.sup.5 or N; R.sup.8, R.sup.9, R.sup.10, R.sup.11 and R.sup.12 are independently, H, an optionally substituted hydrocarbon group, etc., or a salt thereof are also provided. Also specify X.sup.1, R.sup.3, R.sup.1, Y and X.sup.3 in formula (II) and (III) as before.