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Abstract: Acute and prolonged bone complications associated with radiation and chemotherapy in cancer survivors underscore the importance of establishing a laboratory-based complementary dual-isotope tool to evaluate short- as well as long-term bone remodeling in an in vivo model. To address this need, a liquid scintillation dual-label method was investigated using different scintillation cocktails for quantitative measurement of 3H-tetracycline (3H-TC) and 45Ca as markers of bone turnover in mice. Individual samples were prepared over a wide range of known 45Ca/3H activity ratios. Results showed that 45Ca/3H activity ratios determined experimentally by the dual-label method were comparable to the known activity ratios (percentage difference ∼2%), but large variations were found in samples with 45Ca/3H activity ratios in range of 2–10 (percentage difference ∼20–30%). Urine and fecal samples from mice administered with both 3H-TC and 45Ca were analyzed with the dual-label method. Positive correlations between 3H and 45Ca in urine (R=0.93) and feces (R=0.83) indicate that 3H-TC and 45Ca can be interchangeably used to monitor longitudinal in vivo skeletal remodeling. [Copyright &y& Elsevier]