For various reasons the well-known myelopoietic damage caused by cancer chemotherapy is not easy to quantify by means of usual diagnostic procedures. The bone marrow scan with a Tc 99m-nanocolloid rapidly cleared by the phagocytic action of the RES, which has a topographic extension similar to red marrow, has been used for many years to evaluate the inflammatory and neoplastic diseases, both localized and diffuse. Such examination was thus performed in patients undergoing cytostatic therapy, either to follow-up metastatic lesions or to evaluate a tissue damage due to different drugs. The BMS is easily performed and has no side-effects. It consists of a dynamic and a static part. Moreover, it helped pointing out important diagnostic data, such as the reduction of the sacroiliac uptake index below the normal values (3.7) in 33 out of 57 cases, and an abnormal distribution of nanocolloid in the skeleton (Munz's classification, 1983) in 37 out of 69 cases, higher in more myelotoxic cytostatics, which could be detected even after a few months.