1. High resolution 31P nuclear magnetic resonance (NMR) spectra, with and without proton decoupling, of the principal egg phosphoproteins--phosvitins--of a bird (Gallus gallus), an amphibian (Xenopus laevis) and a fish (Salmo gairdneri) were obtained. 2. The spectra were evaluated with special reference to available amino acid sequences and the major NMR resonance in all three spectra was assigned to phosphoserine clusters. 3. The resolution of numerous additional phosphorus resonances provides the basis for further investigation of the particular molecular environments of phosvitin-bound phosphoryl groups and their involvement in the diverse binding modes for metal complex formation by phosvitins.