The contents of this monograph Hypothalamic Control of Lacta tion are the result of studies by a nine-man team which has worked together for nine years. The topic is so fascinating that new research students are attracted to it every year, and the circle is growing steadily. This is, in fact, part of a much more extensive research field to which our Department is applying itself at present, viz. Hypo thalamic Pharmacology . Our work in this sphere was made possible by a generous grant from the United States Department of Agriculture, which helped us during the first 5 years of research with Grant No. FG-IS-147, Project No. A10-AH-3, and recently with another grant for a further 5-year period, No. FG-IS-259, Project No. A10-AH-33. Our thanks are due to Dr. JOEL BITMAN, Hormone Physiology Leader of the USDA Agri cultural Research Service at Beltsville, Md., the sponsor of this research. As this monograph contains mainly references connected with our own work, the reader who wishes to make a survey of lactation should study the references cited in the bibliography, such as COWIE (1961, 1966), COWIE and FOLLEY (1957, 1961), FOLLEY (1952, 1956), JACOB SOHN (1961), LYONS and DIXON (1966), MEITES (1959a, 1961, 1966), MEITES and NICOLL (1966).