Assessment of bone marrow metastases using Tc-99m-labeled antigranulocyte antibodies and Tc-99m-labeled nanocolloids is discussed in osseous metastasizing breast cancer. A 53-year-old patient with bone metastases of breast cancer (pT2 pN1biv cM1) developed leukocytopenia WHO Grade III following polychemotherapy. Bone marrow scintigraphy with Tc-99m labeled nanocolloids and Tc-99m-labeled antigranulocyte antibodies revealed pronounced bone marrow infiltration as the cause. Comparing both procedures, the images with antigranulocyte antibodies showed a clearly better bone marrow image, considerably higher contrast and almost no superimposition of the liver over the spine. In osseous metastasizing breast cancer, scintigraphy with Tc-99m-labeled antigranulocyte antibodies enables assessment of metastases in the entire bone marrow.