Page "Apostolic succession" Paragraph 30

Roman Catholics recognize the validity of the apostolic successions of the bishops, and therefore the rest of the clergy, of the Eastern Orthodox, Oriental Orthodox, Church of the East, and the Old Catholic Church ( Union of Utrecht only ).

The Eastern Orthodox generally recognize Roman Catholic orders, but have a different concept of the apostolic succession as it exists outside of Eastern Orthodoxy.

The lack of apostolic succession through bishops is the primary basis on which Protestant communities are not considered churches by the Orthodox churches and the Roman Catholic Church.