The densities and sound velocities in dilute aqueous solutions of nine N-acetyl amino acid amides were measured at (5, 15, 25, 35, and 45)degrees C. The N-acetyl amino acid amides used were N-acetylglycinamide, N-acetyl-L-alaninamide, N-acetyl-L-valinamide, N-acetyl-L-leucinamide, N-acetyl-L-methioninamide, N-acetyl-L-prolinamide, N-acetyl-L-phenylalaninamide, N-acetyl-L-tryptophanamide, and N-acetyl-L-tyrosinamide. Partial molar volumes and partial molar isentropic compressibilities of these N-acetyl amino acid amides at infinite dilution were evaluated. Furthermore, the side chain contribution to the partial molar quantities of the N-acetyl amino acid amides can be derived using a group additivity approach. The results were compared with those of amino acids reported in our previous paper.