[b] On occasion the promotion declares a championship vacant, which means there is no champion at that point in time.
This can either be due to a storyline,[c] or real life issues such as a champion suffering an injury being unable to defend the championship,[d] or leaving the company.
[e] It was first won by Negro Casas in 1987 and had been defended not only in Mexico but Europe, Japan and the United States as well.
The title was held by many of the top cruiserweight wrestlers of the 1990s including Heavy Metal, Psicosis, Juventud Guerrera, Rey Misterio, Jr. and Eddie Guerrero.
The current champion is El Hijo de Rey Misterio II.