AbstractInvestigations were undertaken to correlate changes in proteins with development and morphogenetic movement of palate shelves in the fetal mouse. Soluble palate proteins were analyzed by polyacrylamide disc gel electrophoresis. Three major groups of proteins were present: (1) three bands at Mx 0.35–0.48 designated αl–3, (2) five bands at Mx 0.70–0.85 designated β1‐5, and (3) one band at Mx 1.0 designated γ. Changes in the relative concentration of some of these proteins occurred during development: by day 15.5 of gestation α3, β4, and β5 had increased while α1, μL2, β1, β2, and β3 had decreased. Comparison of these palate proteins with other fetal and adult tissue proteins indicated that α and γ were probably present in both fetal and adult tissues, but β was present only in fetal tissues. The results showed that α, β, and γ were present in the palate extracellular matrix but β was not found in isolated palate cells. Furthermore, a different electrophoretic distribution of proteins was found for the cell proteins. Further evidence indicated that α and γ were transferrin and albumin, respectively, and that β was a fetal plasma glycoprotein analogous to calf fetuin. The presence of these plasma proteins in the matrix was thought to be due to their circulation throughout the extracellular space of fetal tissues; and the relative change in the proportion of these electrophoretically separable proteins during development to reflect comparable changes in the fetal plasma.