In January 1946, all existing oil refineries and wells situated in the Czech part of former Czechoslovakia were consolidated under Československé naftové závody (ČNZ). In 1948, ČNZ was employing 1,858 workers. In 1958, ČZN merged with a Slovakian oil company to form Moravské naftové doly. The Slovakian section of the company broke away from Moravské naftové doly in 1990.