Iron oxide-based semiconductor gas sensors were exploited for detecting dimethyldisulfide (DMDS) gas, an important flavor component of consomme soup. Among the various metals and metal oxides tested, Pr6O11 was the most effective additive to Fe2O3 for promoting the sensitivity to DMDS vapor (20 ppm) in air at 300°C, giving the highest sensitivity at a Pr6o11 content of 5wt%. The sensor using 5wt%Pr6O11-added Fe2O3 was also fairly good in selectivity to DMDS among various flavor components of consomme soup. As characterized by XRD, 5wt%Pr6O11-added Fe2O3 system contained no crystalline phases other than Fe2O3, while PrFeO3 was observed at Pr6O11 contents of 1Owt% and above. The Pr4+/Pr3+ ratio as revealed from XPS analysis remained far higher for Pr6O11-added systems than that for pure Pr6O11, though it tended to decrease with increasing Pr6O11 content. These results suggest that, at low Pr6O11 contents, a major part of Pr components added exist as finely dispersed Pr4+ species on the surface of Fe2O3 particles and that such surface Pr4+ species are responsible for the observed enhancement of gas sensitivity to DMDS.