Vascular cells and leukocytes, involved in the development of atherosclerosis, produce cytokines and/or reactive oxygen species (ROS) and matrix metalloproteinases (MMPs) implicated in cell mobility. We investigated by co-culture experiments the effects of human coronary smooth muscle cells (HCSMC) on MMPs characteristics and mobility of neutrophil-like dimethyl sulfoxide-differentiated HL60 cells (≠ HL60). The effects of superoxide dismutase (SOD) and catalase were also analyzed. All the studied MMP2 characteristics remained unchanged. HCSMC stimulated MMP9 protein level, activity and mobility of ≠ HL60 cells and expressed and secreted a variety of cytokines implicated in atherosclerosis. SOD and catalase increased MMP9 expression, protein level and activity of ≠ HL60, but migration of ≠ HL60 cells was only decreased by catalase, demonstrating that ROS are more efficient in modulating MMP9 activity of ≠ HL60 than their mobility. Finally, HCSMC being able to stimulate ≠ HL60, their co-cultures may represent an in vitro approach to study cellular interactions occurring in vivo during atherosclerosis.