The proteins and peptides of immature enamel were extracted from freshly slaughtered bovine embryos in solutions containing protease inhibitors. No detectable differences were noted in the number of components, their overall amino acid composition, or molecular weights from the proteins and peptides extracted 12-16 h postmortem in solutions which contained no protease inhibitors. These data indicate that the large number of components found in developing bovine enamel is not due to proteolysis occurring during their isolation. Significant amounts of protein components having molecular weights greater than approximately 15,000 were not detected. Therefore, if the ameloblasts initially synthesize only a few high molecular weight protein species, the present data imply that in vivo degradation of the high molecular weight enamel proteins occurs very rapidly after their synthesis and precedes the massive loss of protein which accompanies the final stages of enamel mineralization and maturation.