MACROPHAGES IN REGRESSING AND PROGRESSING MOLONEY SARCOMAS**This is manuscript number 996 from the Department of Immunopathology, Scripps Clinic and Research Foundation, 476 Prospect Street, La Jolla, California 92037. The work was supported by USPHS contract N01-CB44001; USPHS grants AI 07007 and CA 17720; California Division-American Cancer Society Junior Fellowship J-235; and the Lilly International Fellowship Foundation. The authors thank Mr. Ronald Hoskins and Ms. Ann Tozier for their excellent technical assistance.