Geraldo was born in Sonora, Mexico, and fought out of Baja California for much of his career.[1][2] Geraldo's first professional fight was in September 1970, a points defeat of Albaro Parra. In 1977 he won the Mexico middleweight title, defeating Emetrio Villanueva by a knockout. After two successful defences he moved up to the light heavyweight division, beating David Cabrera to become Mexico light-middleweight champion in November 1982.[3] He also won the California State Middleweight title in 1978.
In 1979 he suffered a points defeat to Sugar Ray Leonard over ten rounds, with the same result a year later against Marvin Hagler.[4] He was ranked in the top ten by both the WBC and WBA in 1980.[5] He fought Thomas Hearns in 1982, losing by a first round knockout.[6][7] Leonard ranked his fight with Geraldo as his fourth toughest, behind those against Hearns, Wilfred Benítez, and Roberto Durán, and regarded Geraldo as the hardest puncher he had fought.[8][9] In 1985 Geraldo drew with Prince Mama Mohammed in a Stroh's Cruiserweight Championship fight, and lost to Michael Nunn by a fifth round TKO.[10][11] He fought Virgil Hill in 1987, losing by a second round knockout. He continued fighting until 1995, losing his final fight to Leonardo Aguilar.
He also lost to Angel Robinson Garcia.
Over his 25-year professional career he won 66 of 95 fights, 47 by knockout.
His son, Marcos Antonio López, is also a professional boxer.