In organic/metal interfaces systems involving complex organic molecules or polymers, the effect of the physical interfaces can be extend further than a monolayer into the organic film. An example of such an effect is the preferential orienting of large molecules at a surface and thier subsequent stacking into the near-interface region. Reflection-absorption infrared spectroscopy, RAIR, is uniquely suited to studying such psuedomorphism on metal substrate. Unlike previous qualitative applications of RAIR, however, it is used in a quantitative mode in the two applications discussed here. In these applications the organic systems are very different but the approach taken to extract structural information at the interface is the same. RAIR spectra are obtained from very thin films with thickness being the parameter being varied. The interface region makes a larger contribution to the overall spectrum as the thickness decreases. By observing the “thickness” -normalized band absorbances as a functioning of “thickness”, the percentage band intensity changes can be determined in going from the randomly oriented thick or bulk film case to the ordered thin film case. Given the RAIR selection rule that only dipole moment changes perpendicular to the surface can be observed and a reliable knowledge of the band assignments and transition moment directions in the organic molecule, the changes can be interpreted in terms of a specific orientation and conformation at the interface. This method of RAIR data sampling and analysis is refered to as quantitative absorption-reflection thickness IR or QUARTIR. In the first example, thin films of the photo-masked surfactant (PMS) 4, 5 dimethoxy-2 nitrobenzyl hexadecane sulfonate, solution cast in a copolyester matrix onto air oxidized Al substrate were studied. PMS to polyester weight ratios of 1:2 were used with estimated total film thicknesses varying from ca. 100 to 1000 Å. By digitally substracting out the stronger PE contribution from the combined spectra using plain PE preference sample spectra, the PMS spectra alone could be monitored as a function of thickness. From the fractional changes in the “thickness” -normalized intensities of 17 major bands upon going from the randomly oriented bulk state to the oriented interface state, the angles between the surface normal and the various transition moment directions could be deducted self-consistently. The resulting model of the blocked surfactant that preferentially diffuses to and orients at the Al oxide interface has the aromatic ring plane perpendicular to the surface with one nitro oxygen pointing towards it, leaving the hydrocarbon tail pointing away from the surface. The perpendicular bisector of the NO 2 group is inclined 30°C with respect to the surface normal. The preferred orientation of the SO 2, OCH 3 and S-O-CH 2 groups are also determined to be consistent with this model. In the second example thin films (30–1400 Å) of the photosensitive dye perylene red (PR) or N, N-Di (3, 5-xylyl) perylene-3, 4:9, 10 bis (dicarboxyimide), and metal free phthalocyanine (H 2Pc), were vacuum sublined onto air oxidized, sputter deposited Al substrates. From the strong monotonic variations in the “thickness” normalized relative band absorbances as the interface is approach, it can be concluded that at the interface the PR molecules are preferentially oriented such that all have thier major symmetry plane perpendicular to the surface. A unique orientation exists within that plane for a single molecular stack model and specified ranges of paired angles for a model of two stacks of differently oriented molecules. This behavior is in contrast to the H 2Pc films which appear to remain disordered down to ca. 100 Å.