To the Editor.— The results of Cronenwett et al1 are interesting for the answers they provide and the questions they generate. Most striking in their discussion is the authors' dismissal of "nipple confusion" in light of the timing of their investigations into the effect of regular bottle-feedings for breast-feeding infants. I have observed that infants who are exposed to rubber nipples before they have learned how to effectively suckle the human breast2 seem to try to use the breast as if it were a rubber nipple.