The chapter presents a survey on the possibilities of determination of the age of archaeological samples containing proteins based on the transformations of amino acids therein. The first possibility is to estimate the chronological age based on the extent of racemization of the L-amino acids, which are the constituents of native proteins. In 1967, Hare and Abelson reported that D-amino acids present in fossils resulted from the conversion of L-amino acids of protein. It was found that the older the fossil, the higher the D/L ratio and, after a certain age, amino acids occurred in the racemic form. The ratio of D-allo-isoleucine and L-isoleucine content in a fossilized shell sample was found to be 0.32, and the fossil was estimated to be 70,000 years old. Another method is used for the determination of age at death based on the racemization of aspartic acid in teeth. In addition to aspartic acid, D-glutamic acid was also found to be suitable for the estimation of age. Calibration curves based on these investigations were used for the age estimation of more than 200 skeletons of unknown age from different historical periods. The correlation coefficient between the results and those obtained using standard paleoanthropological methods was over 0.9. Experiments show that the later forming teeth racemized more slowly than those which erupted earlier, and this must be taken into consideration for age determination. Comparative experiments suggest that differences in the extent of racemization of the same individual can be larger than the difference between individuals.