This review describes the potential role of macrophages in defense against cancer cells and the regulatory involvement of inflammatory mediators in this role. Interactions between macrophage-derived cytokines (tumor necrosis factor alpha, interleukin-1, IL-6) and their interrelationships with eicosanoids (mainly the cyclooxygenase product prostaglandin E2 and some lipoxygenase metabolites) represent a network that controls the expression of antitumor activity of macrophages either in a cell-to-cell contact system between the effector and the target tumor cell or as cell-free soluble products. Attention is given to the influence of tumor burden on production of cytokines and eicosanoids by macrophages and to the production of these mediators by tumor cells. Emphasis is placed on the roles of TNF-alpha and PGE2 in links between inflammatory and antitumor functions of macrophages. Finally, the perspectives and still existing problems in clinical implications of macrophage-derived cytokines are discussed in terms of a conceivable macrophage-directed immunotherapy of cancer.