Following the observation of the diffuse absorption bands near the second member of the principal series of Rb and Cs by Ny and Chen in the presence of foreign gases, we were led to study the absorption spectrum of sodium in the presence of nitrogen and hydrogen with a Hilger E-316 quartz spectrograph and a 10-foot grating spectrograph of Eagle mounting. Corrosion resistant MgO windows were used in the absorption tube so that both the absorbing and the perturbing atoms within the absorbing column had a homogeneous concentration. Diffuse absorption band was observed only by the shorter wave-length side of the third member of the principal series but not by any of the others. The separation between the intensity maximum of the diffuse band and the principal lines is larger in the case of hydrogen than that of nitrogen. They are 3.48 A for nitrogen and 4.17 A for hydrogen. The wavelength of the intensity maximum of these bands are respectively 2849.4 A and 2848.7 A for nitrogen and hydrogen.