The control of milk synthesis depends on a complex interaction of autocrine and endocrine factors. The contributions of these two systems are continually being clarified by research. This presentation explains the two systems, their interactions, and what this means for the advice we give to mothers. Should an engorged mother pump? How do we best help a mother increase milk supply? How do we control oversupply without increasing the risk of mastitis? The scientific background is clearly delineated in understandable language, and these quandaries discussed.