The possible transfer of learning performance by proteins and ribonucleic acids was studied. 140 male Sprague-Dawley rats aged 3 months and 68 aged 20 months were used. Proteins and ribonucleic acids were isolated from the brains of trained and untrained rats aged 3 months. The difference in learning performance was tested and the incorporation of the above-mentioned substances into the hippo-campus and the residual brain in the two age-groups was measured using radioactive labelled material. A specific transfer of learned information-contents on the molecular level was found only after transfer of proteins in both young and old rats; the results of the training are well correlated with those of the incorporation. The two age-groups differ especially with regard to the learning performance, expressed in the error number. In th older group the error number is significantly lower in contrast to the learning time, that is slightly shorter in the younger group. This can be explained by the differences between the incorporation of brain proteins of trained animals into animals of different age, as well as by the investigations of some authors, who distinguished between different modes of learning. The lower incorporation of labelled substance into the brains of old animals is remarkable; the conclusion is a lower turnover of these substances in the brain of old animals, especially of the ribonucleic-acids. Nevertheless the learning performance of complex information-contents is not impaired.