There are three kinds of sacred oils, all of which signify the work of the Holy Spirit, who "serves to sweeten, to strengthen, to render supple". The three holy oils are:

  • The Oil of Catechumens is used in Baptism along with water, in the consecration of churches, in the blessing of Altars, in the ordination of priests, and, sometimes, in the crowning of Catholic kings and queens.
  • The Holy Chrism is olive oil mixed with a small amount of balm or balsam. It is used in Confirmation, Baptism, in the consecration of a Bishop, the consecration of various things such as churches, chalices, patens, and bells.
  • The Oil of the Sick is used in Annointing the Sick.

The blessing of oils is performed by the Bishop of each diocese on Maundy Thursday ("Holy Thursday") in the diocese's cathedral during a "Chrism Mass." The oils are kept in metal or glass bottles called "chrismatories," "chrismals," or "ampullae." These vessels are then stored in a cabinet called an "ambry," which is usually fixed to the wall of the sanctuary. Priests also have a portable "oilstock" which has a section for each of the three holy oils. Lay people are not to handle the holy oils, even to carry them, except in emergencies.