We have developed a method to analyze quantitatively the biochemical composition of human coronary artery in situ using near infrared Raman spectroscopy. Human coronary arteries were obtained from explanted hearts after heart transplantation. Samples of normal intima/media, adventitia, non-calcified and calcified plaque were illuminated with 830 nm light from a CW Ti:Sapphire laser. The Raman scattered light was collected and coupled into a 1/4 meter spectrometer that dispersed the light onto a liquid nitrogen cooled, deep-depletion CCD detector. Raman spectra with sufficiently high S/N for extracting biochemical information could be collected in under one second. The spectra were analyzed using a recently developed model to quantitate the relative weight fractions of cholesterol, cholesterol esters, triacylglycerol, phospholipids, protein, and calcium salts. After spectral examination, the artery samples were biochemically assayed to determine the total lipid weight and the amount of the major lipid categories as a percentage of the total lipid content. The results of the lipid biochemical assay and the Raman spectral model compare favorably, indicating that relative lipid weights can be accurately determined in situ. Protein and calcium salts assays are underway. This in situ biochemical information may be useful in diagnosing atherosclerosis and studying disease progression.