[en] This study was initiated to determine health effects resulting from inhalation of ⁹⁰Sr in relatively insoluble form. Beagle dogs were briefly exposed by inhalation to produce lung burdens of ⁹⁰Sr that ranged from 0.12 to 96 μCi (4.4-3500 kBq)/kg body weight. Exposures to the higher concentrations of ⁹⁰Sr caused radiation pneumonitis and pulmonary fibrosis, typically resulting in death < 500 days after exposure. Exposures to lower concentrations are producing longer term health effects, including cancer of the lung, heart, and tracheobronchial lymph nodes. Most tumors have been hemangiosarcomas. Three ⁹⁰Sr-exposed dogs were euthanized during the past year. One remaining exposed dog and one control dog are both 14 yr old and are being maintained for lifetime observation. (author)