Monodeuterated derivatives of;the salts of tyrosine, valine, glycylglycine, and glycylglycylglycine are investigated by infrared spectroscopy. Irradiation in the spectral region of the N-D stretch bands produces spectral holes and antiholes. These result from rotation of N-D-containing moieties. The holes and antiholes identify the vibrations of the amino group and provide information on the hydrogen-bonding environment. Both the various amino acid salts and the two peptide salts hole burn, suggesting that infrared hole burning will provide a useful tool for investigating a range of biologically interesting materials.