WO3 and Cr-WO3 powders were prepared by sol-gel process, with Cr: W atomic concentration ranging from 2% to 8.8%. WCl6 was used as W precursor and reacted with methanol in presence of acetyacetone as stabilizer. The required amount of Cr 2-ethylhexanoate was then added to the resulting solution, which was then dried. The resulting powder was heat-treated at temperatures ranging from 200 to 700 C. With increasing the Cr concentration, the samples heat-treated at 500 C contained an increasing amount of the additional phase Cr2WO6. The analysis of the X-ray diffraction and Transmission Electron Microscopy data showed that the use of the Cr 2-ethylhexanoate precursor seemed to favor Cr incorporation in interstitial position in the WO3 lattice. The sensing tests towards ammonia gas, from 50 to 500 ppm, showed that, up to 5% concentration, Cr addition lowered the best operating temperatures and/or …