Silver selective electrodes based on thioether functionalized calix[4]arenes 1 and 2 as ionophores were investigated. For both ionophores the selectivity coefficients (log k A g , M ) were lower than -2.2 for Hg(II) and lower than -4.6 for other cations tested. The best results were obtained with membranes containing dithioether functionalized calix [4] arene (ionophore 2), potassium tetrakis(4-chlorophenyl)borate (KTpClPB) and bis(1-butylpentyl)adipate (BBPA) as a plasticizer. The Ag(I)-response functions exhibited almost theoretical Nernstian slopes in the activity range 10 - 6 -10 - 1 M of silver ions.