Studies have suggested the role of cytokines in inflammation, as determined by results obtained in vitro, or with assessments of clinical samples. However, extrapolation of in vitro results to an in vivo situation must be made with caution, and findings obtained from clinical samples tend to lack a causal relation between cytokines and inflammatory responses. Animal models of inflammation can be useful in understanding roles of cytokines at sites of inflammation. We examined the production kinetics and cellular sources of tumor necrosis factor alpha (TNFalpha), interleukin (IL)-1beta, IL-8, and IL-1 receptor antagonist (IL-1Ra), and obtained evidence for the involvement of these cytokines in a rabbit model of arthritis induced by lipopolysaccharide (LPS). We also attempted to analyze the inflammatory cytokine network among TNFalpha, IL-1beta, IL-8, and IL-1Ra. Understanding the role of cytokines in animal models paves the way to a better understanding of disease in humans.