The chapter "Secretory Products of Macrophages" by Carl F. Nathan discusses the extensive and diverse array of substances secreted by macrophages, highlighting their crucial role in immune and inflammatory responses. Macrophages, found in various tissues and organs, are involved in phagocytosis, wound healing, and the regulation of inflammatory responses. The chapter emphasizes that while macrophages produce a wide range of products, many of these products have multiple functions and can be produced by other cell types as well. Key topics include the molecular definition of macrophage products, the multiple activities of individual products, and the interactions among different products. The review also explores the sources of these products and the mechanisms by which macrophages regulate their secretion. Finally, it outlines future research directions to better understand the complex functions of macrophage secretory products.The chapter "Secretory Products of Macrophages" by Carl F. Nathan discusses the extensive and diverse array of substances secreted by macrophages, highlighting their crucial role in immune and inflammatory responses. Macrophages, found in various tissues and organs, are involved in phagocytosis, wound healing, and the regulation of inflammatory responses. The chapter emphasizes that while macrophages produce a wide range of products, many of these products have multiple functions and can be produced by other cell types as well. Key topics include the molecular definition of macrophage products, the multiple activities of individual products, and the interactions among different products. The review also explores the sources of these products and the mechanisms by which macrophages regulate their secretion. Finally, it outlines future research directions to better understand the complex functions of macrophage secretory products.