Macrophage inflammatory protein-1 alpha (MIP-1alpha) is a chemokine primarily associated with bone absorption. We examined whether MIP-1alpha was produced by purified fresh tumour cells isolated from bone marrow samples from 31 multiple myeloma (MM) patients. High levels of MIP-1alpha were found in supernatants of myeloma cell cultures. Immunohistochemical staining showed MIP-1alpha in the cytoplasm of myeloma cells. MIP-1alpha mRNA expression was detected in 18 of 31 patients. Bone lesions were seen in 16 of the 18 MIP-1alpha-positive patients but only in six of the 13 MIP-1alpha-negative patients (P = 0.0097,chi2-test). The data indicate that MIP-1alpha is produced by myeloma cells and possibly plays a role in the pathogenesis of bone lesions in MM patients.