The aim of this review is to introduce the adverse health effects of indium compounds. This review consists of 2 parts: (1) a study of the toxic effects of indium compounds in humans, and (2) a study of the toxic effects of indium tin oxide (ITO) and copper indium gallium diselenide (CIGS) in animals. To date, 4 epidemiological surveys have been conducted of indium-handling workers in Japan, and all who were studied showed that exposure to indium compounds caused pulmonary interstitial and emphysematous changes. There were clear dose-response and dose-effect relationships between the serum indium levels and the levels of Krebs von den Lungen-6 (KL-6), which is a serological indicator of interstitial pneumonia. Up until 2011, 8 cases of interstitial pneumonia in Japanese indium-exposed workers, 2 cases of pulmonary alveolar proteinosis (PAP) in US indium-exposed workers, and 1 case of PAP in a Chinese indium-exposed worker have been reported. In animal studies, it has been clearly demonstrated that ITO and CIGS particles cause pulmonary toxicity and that the dissolution of ITO and CIGS particles in the lungs is considerably slow when repeated intratracheal instillations were given to experimental animals. Thus, more studies are needed on the effects of human exposure to indium compounds.