The essay deals with number of issues related to the Hephaestio’s method of compilation. Focusing on his abbreviation of theoretical chapters of Ptolemy's Tetrabiblos (I, 1-3, and III, 2), it traces the changes that were explicitly introduced by the later author to the existing text as well as those caused by the abbreviation itself. As a consequence of all these modifications, the later author looses much of the philosophical and scientific consistency of his predecessor, proving simultaneously quite indifferent to the principle of systematic arrangement so important to Ptolemy.