In this paper, ammonia-sensing behavior of barium strontium titanate (BST) thin films have been reported for the first time. Thin films of BST deposited by sol-gel spin coating technique have been found to show an increase in resistance when exposed to ammonia gas. The sensitivity variation was from 20 to 60%, with lowest detection limit of about 160 ppm. The films were prepared with different pre-sintering temperatures and thickness and effect of these parameters on the ammonia-sensing have been studied. The optimum temperature for operation was found to be close to 270 °C. The ammonia-sensing studies were also performed for other gases like ethanol, NO2 and CO; but the sensitivity in these cases was negligibly smaller than that in case of ammonia. © 2005 Elsevier B.V. All rights reserved.