The priest wears the epitrachelion whenever he is serving as a priest. For some services, e.g., Vespers or Orthros, he wears the epitrachelion by itself. When he is fully vested for the Divine Liturgy, he wears the epitrachelion over the sticharion and under the zone and the phelonion. If a priest is simply attending a service, he wears no liturgical vestments, but will put on his epitrachelion (and in Slavic traditions, his epimanikia) before receiving the Eucharist.