The past decade has seen the emergence of two new paradigms in inflammatory disease: first, cardiovascular complications of atherosclerosis are markedly increased in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE); and second, inflammatory mechanisms are important in the pathogenesis of atherosclerosis. These concurrent developments have lead to the concept that inflammatory mediators operative in RA and SLE might be causal in the accelerated atherosclerosis observed, a concept supported by clinical studies showing that this acceleration is not fully explained by traditional vascular risk factors. Separate lines of evidence implicate the cytokine macrophage migration inhibitory factor (MIF) in RA, SLE, and atherosclerosis. Several reports have revealed definitive in vivo evidence of the activity of MIF in a model of SLE, demonstrated a novel role for MIF in monocyte/macrophage recruitment, and showed that MIF regulates a key mediator of inflammatory cell activation. Together with evidence that MIF circulates in increased concentrations in patients with RA and SLE, this information suggests that in addition to contributing to each disease, MIF might contribute directly to the acceleration of atherosclerosis in RA and SLE.