In 1949 and 1950, Dudley and his associates (1, 2) showed that radiogallium 72 concentrated in areas of osteogenic activity, but Brucer et al. (3) subsequently demonstrated the impracticability of use of the isotope therapeutically because of toxicity of the non-radioactive carrier. Later, Desgrez et al. (4) investigated further the distribution of radioactive gallium in the skeleton and particularly in bone tumors. More recently Bauer and his co-workers (5, 6) found a high uptake of Sr85 by external counting over skeletal lesions such as fractures, metastatic carcinoma, eosinophilic granuloma, chondroma, osteomyelitis, and Paget's disease. In 1961, Fleming and his group first demonstrated the use of Sr85 for the photoscanning of bone lesions (7). Strontium 85 is admirably suited for photoscanning since, in its decay by electron capture to stable rubidium 85, a single gamma photon of 0.51 Mev is emitted. The material is administered intravenously, 50 µc to adults and 20 µc to patients under twenty years of age. The estimated total body dose to a standard man is 0.325 rads and the bone dose is 2.28 rads (7). Strontium 85 is obtained2 as the nitrate in 0.91N nitric acid solution, with specific activity of 2,720 mc per gram or greater. Purity is of the order of 98 per cent, with less than 1 per cent strontium 89. The material is not neutralized but merely diluted appropriately and administered intravenously. Approximately twenty-four to forty-eight hours later, the patient is scanned with the Picker magnascanner equipped with a 3 × 2-inch thallium-activated sodium iodide crystal and a 19-hole focusing collimator. Case Reports Case I: M. F., a 64-year-old white male, complained of pain in the right femur of one month duration. X-ray studies revealed an osteolytic lesion of the middle third of the shaft of the femur (Fig. 1). A photoscan with radioactive strontium was performed and the lesion was visualized as it appeared on the film. Subsequently, a biopsy was reported as showing metastatic carcinoma, probably from the lungs. Case II: R. A. N., a 45-year-old Negro female, was admitted to the hospital Oct. 1, 1962, complaining of pain and swelling of the left knee of four months duration. During this time, several x-ray examinations failed to reveal any abnormality. In spite of medical treatment, the pain persisted and gradually increased in severity so that at the time of admission it was constant. In May 1961 a right hemicolectomy had been performed for carcinoma. In view of this history and the persistent pain, a scan with radioactive strontium was performed, revealing a localized area of uptake in the region of the head of the tibia. Accordingly, an open bone biopsy was carried out and the pathologist reported the presence of adenocarcinoma consistent with metastasis from the colon.