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Abstract Objective  Bone metastases occur in ∼80% of patients with advanced cancer and cause significant morbidity. There are currently no established means by which to identify the early growth of micrometastatic cells or their effects on bone at a time when curative therapy might be initiated. We postulated that high-resolution magnetic resonance imaging (MRI) could detect and quantify the growth and destructive effects of bone micrometastases. Design  Using a mouse model for metastasis of malignant melanoma, we have examined the ability of MRI to quantify cortical bone destruction and the percentage of the medullary cavity occupied by tumour, trabecular bone, and marrow. The results from MRI were compared to histomorphometry (the reference standard) and to radiographs. Results  In vivo gradient-echo and spin-echo MRI demonstrated that metastatic melanoma replaced the marrow space but that the cortical bone integrity was preserved (P ≤ 0.001). The smallest detectable micrometastasis had an area of 0.323 mm2. In contrast, we observed no trends after quantifying the radiograph data. Conclusion  These approaches delineated the limits of MRI in its ability to quantify tumour burden and the effect on bone in this model. Given the increasing use of MRI as a non-invasive clinical diagnostic method, the present findings may be applicable in detecting bone metastases in the clinical setting at an early and potentially treatable stage. [ABSTRACT FROM AUTHOR]