SIR-The origin of the diffuse interstellar absorption bands remains an unsolved problem after more than 50 years of research1• 2• Here I draw attention to a set of four emission features from the biconical nebula of the Red Rectangle3, the wavelengths of which correspond well with those of a recently classified subgroup of diffuse interstellar absorption bands4. It is thought that at least one of the diffuse band carriers is formed in the Red Rectangle region. The diffuse interstellar band spectrum consists of over forty absorption features in the visible spectral region, with a wide variety of intensities and widths 1• On the basis of the relative strengths of a number of bands along different lines of sight, it has been suggested4 that they can be divided into families, one of which includes those bands occurring at wavelengths of 5,797, 5,850, 6,376, 6,379 and 6,614 A. These bands are reasonably strong and comparatively narrow, their line widths being in the region of 1 A. The Red Rectangle emiSSIOn spectrum has an unidentified set of broader emission features with peak wavelengths of spatially integrated spectra near 5,799, 5,855, 6,380 and 6,615 A (ref. 3) and typical widths of about 6 A. These two sets of wavelengths are in remarkably good agreement and the greater widths and small wavelength shifts of the Red Rectangle bands relative to the diffuse interstellar bands can be attributed to the higher temperature close to the star HD44179. Also, the profiles of the bands in absorption (diffuse interstellar bands, DIB) and emission (Red Rectangle, RR) are qualitatively similar; the 5,797 (DIB5) and 5,799 (RR) profiles have a steep blue side, the 6,379 (DIB5) and 6,380 (RR) bands have approximately symmetrical profiles, and the 6,614 (DIB6) and 6,615 (RR) bands also have a steep blue side. The notable absence