This study was initiated because of a suspected increase in incidence of lung cancer in antimony smelter workers in England. Three groups of 8‐mo‐old Wistar‐derived rats (90 males and 90 females per group) were exposed by inhalation to either Sb2O3[time‐weighted average (TWA) 45 mg/m3], Sb ore concentrate (TWA 36 + 40 mg/m3), or filtered air (controls) for 7 h/d, 5 d/wk, for up to 52 wk and sacrificed 20 wk after terminating exposures. Serial sacrifices (5 rats/sex/group) were performed at 6, 9, and 12 mo. Autopsies and histopathological examinations were performed on all animals. The dusts and animal tissues were analyzed for Sb, arsenic, and other inorganic elements by atomic absorption and proton‐induced X‐ray emission methods. The most significant findings were the presence of lung neoplasms in 27% of females exposed to Sb2O3and 25% of females exposed to Sb ore concentrate (p < 0.01). None of the male rats in any group or the female controls developed lung neoplasms. There were no significant differences in incidences of cancer of other organs between exposed and control rats. These results were compared with other published results, including an animal inhalation study with Sb2O3in which lung tumors were also induced