Iridium oxide thin films with variable thickness were deposited by spray pyrolysis technique (SPT), onto the amorphous glass substrates kept at 350degreesC. The volume of iridium chloride solution was varied to obtain iridium oxide thin films with thickness ranging from 700 to 2250 Angstrom. The effect of film thickness on structural and electrical properties was studied. The X-ray diffraction (XRD) studies revealed that the as-deposited samples were amorphous and those annealed at 600 degreesC for 3 h in milieu of air were polycrystalline IrO2. The crystallinity of Ir-oxide films ameliorate with film thickness thereby preferred orientation along (110) remains unchanged. The infrared spectroscopic results show Ir-O and Ir-O-2 bands. The room temperature electrical resistivity (rho(RT)) of these films decreases with increase in film thickness. The p-type semiconductor to metallic transition was observed at 600degreesC. (C) 2003 Elsevier Science B.V. All rights reserved.