In the present article author’s considerations on a fundamental economic problem are carried out, and results and conclusions, arising out of author’s investigationsр, are discussed. The problem of the depreciation of fixed assets has always been central to the accounting science, the economy and society. The article attaches importance to fundamental scientific research works, emblematic for the Bulgarian accounting science in its classical (pre-Second World War) period, during which the theoretical and methodological bases of the problem of the depreciation of fixed assets were developed. The article highlights, analyzes and summarizes views of distinguished theoreticians of the depreciation problem, that have most substantially influenced the process of developing and systematizing specialized accounting knowledge on depreciation. On the bases of the retrospective comparative analysis, it is argued that the foundational research and conceptual ideas of the classical period and later, have contributed to a considerable expansion and enrichment of the system of knowledge in this scientific field.