In the diagnosis of multiple myeloma (MM), the radiological skeletal survey (RSS) was proven to be most useful for the detection of bone lesions. Since 1961, a new technique radioisotopic bone scan (RIBS), for the detection of such lesions, using 85Sr and 99mTc, has been shown to be highly sensitive for the detection of skeletal metastases of epithelial tumors. We have studied 30 patients with plasma cell dyscrasia (PCD) by both methods and concluded that RSS is clearly superior to RIBS in PCD. As RIBS detected less than 50% of the lesions demonstrated by RSS there seems to be no indication for a routine RIBS in the initial work-up of patients suspected to have PCD. However, due to the fact that RIBS is useful for the detection of new bone formation it has a certain value in the localization of pathological fractures in MM, mainly in vertebral compression.