Elevated industrial production and broaden applications of indium oxide materials have increased concerns over the occupational exposure of industry workers. Respirable In₂O₃ particles have been identified in the workplaces and lung of indium-processing workers. The aim of this study was to assess the indium distribution and organs injury induced by nano-In₂O₃ particles. More than 50% of nano-In₂O₃ particles were accumulated in the lungs after 8-week exposure period and caused serious pulmonary alveolar proteinosis (PAP) and pneumonia. The migration of nano-In₂O₃ particles from lungs to the other organs was very low and dose not steadily increase the indium burden in those organs except kidney and liver. The repeated intratracheal instillations of nano-In₂O₃ particles into the lungs of Wistar rats were dose-dependent increased the concentrations of serum indium.