A general introduction by John Dillon. An annotated Russian translation of theIntroduction to Arithmetic and Manual of Harmonics by Neopythagorean philosopher Nicomachus of Gerasa, prepared by Andrej Schetnikov [Introduction], Timothy Myakin, and Ludmila Alexandrova [Manual]. These short treatises, important for the history of ancient mathematics and musical theory, is completely translated into Russian for the first time.