The Macrophage in Neoplasia is a compilation of papers presented at a workshop held at the Marine Biological Laboratory, Woods Hole, Massachusetts, on October 8-11, 1975. The book presents the many faceted activities of macrophage. This book is divided according to the five sessions of the workshop. First session talks about the role of tumor macrophages in vivo. It then elucidates the macrophage function and indicates how the interaction of macrophages with other cells can alter the host-tumor balance. The remaining sessions, as presented in this book, explore the mechanism of macrophage mediated cytotoxicity, functional expression of macrophages and neoplasia, and the stimulation of macrophage function and applied therapy.