This study was undertaken to determine the occurrence of uronic acid in chicken eggshell membranes and to compare chemical compositions among the inner and outer eggshell membranes and the organic matter of eggshell. We report here for the first time the occurrence of uronic acid in chicken eggshell membranes. Uronic acid concentrations were similar (P > 0.05) between the inner shell membrane and outer shell membrane but approximately fivefold higher (P < 0.05) in the organic matter of eggshell. Sialic acid concentrations were the highest (P < 0.05) in the organic matter of eggshell and higher (P < 0.05) in the inner than in the outer shell membrane. Nitrogen concentrations were the lowest (P < 0.05) in the organic matter of eggshell but relatively constant between the two shell membranes. Amino acid analysis showed that the contents of glycine and alanine were higher (P < 0.05) and those of proline and hydroxyproline were lower (P < 0.05) in the organic matter of eggshell compared to shell membranes.