After the lungs and liver, the bone is the third most common site for metastatic disease, appearing frequently in breast and prostate malignancies. These pathological bone events that occur during the evolution of the metastatic disease are usually the onset of osteolysis and they lower the patient's life quality, and are sometimes the cause of death due to the required treatments (surgery, radiotherapy). Due to the nature of the bone remodeling process, the markers that control bone resorption are the main early indicators of bone malignancy. These markers can be found in excess quantities of 50-150% in patients with bone metastases. Analyzing these indicators in conjunction with traditional tumoral markers such as the prostate specific antigen (PSA) and the type I collagen cross-linked telopeptide (ICTP) can often increase the sensibility of the investigation and the chances of diagnosing bone metastases. The studies that were carried out in order to research this area of knowledge have had good and expected results. Most of the efforts are now channeled into developing a better therapeutic strategy that would allow for the early diagnosis and treatment of the pathological bone events. Until these markers can be used as standard investigation methods in all of our patients, some controlled studies must be carried out in order to statistically prove these results, which are purely observational.