Potassium and caesium ion-selective electrodes (ISEs) have been fabricated from poly(vinyl chloride) matrix membranes containing nine different calixarene-based ionophores. They were used with 2-nitrophenyl octyl ether as plasticising solvent mediator. An anion exchanger [potassium tetrakis (4- chlorophenyl) borate] was included in the ISE membrane construction in some electrodes. The electrodes studied so far showed excellent response characteristics, i.e. near Nemstian response over a wide concentration range (lxl0 4M to lxlCHM). Selectivity coefficients were determined for nine metal cations. The best sensor had a lifetime of more than ten months and a dynamic response times was less than 9 seconds (t90%). Some preliminary results on the performance of solid-state potentiometric sensors based on new materials are also included. These are based on polymeric calixarenes, which have the advantage of producing devices with the active component bonded to the substrate surface. This can simplify the manufacture of the sensors, and prevent the gradual leaking of the active component into the sample. Subsequent to this, the electrodes properties were evaluated by focusing on the stability of their potential response, selectivity, lifetime, and pH dependence. In the final part of this research a chromogenic calix[4]arene was investigated as a lithium or sodium ion selective indicator system. Colourless solutions of the ligands in THF changed lo a yellow colour upon contact with Li+ or Na+ (LiCl, LiC104 or NaCl or NaC104, but not other salts) in the presence of morpholine as a base. It was found that nitrocalix[4]arene was a suitable indicating system capable of detecting lithium and sodium ions over a wide concentration range. The colour density was concentration dependent. These chromogenic compound could have important application in the fabrication of new opto-sensor for sodium and lithium.