In this study, the nanosized arsenic sulphide As4S4 particles have been prepared by mechanical activation in a planetary mill. The bulk and surface properties of the milled particles were characterized by XRD and XPS methods as well as by surface area and particle size distribution measurements. For assessment of arsenic sulphide biological activity, the viability tests of multiple myeloma cancer cells have been applied. The obtained results show the arsenic sulphide nanoparticles properly milled and modified by mechanical activation can be valuated as a potential drug for cancer treatment. (C) 2011 Elsevier B.V. All rights reserved.