Viloria, 25, started like a house on fire and showed little respect for Aguirre whom he attacked furiously as if looking to repeat his first round demolition of Eric Ortiz to wrest the WBC crown in Los Angeles last September.
But Aguirre, 30, proved too experienced, resilient and slick. He took Vilorias best shots and came back to fluster the Hawaii-born Filipino in the second and third rounds which the three judgesRay Hawkins, C. J. Ross and Glenn Trowbridgescored for the Mexican veteran.
Viloria soon realized he was up against a determined challenger who wouldnt go down easily like Ortiz. As the fight wore on, Aguirre clearly earned Vilorias respect.
However, there was no question who was the superior fighter. Viloria finally found his rhythm in the seventh round as Aguirre began to tire and miss. The 2000 Sydney Olympian threw dizzying combinations, backed up Aguirre and dominated the exchanges from the seventh to the 11th roundswhich he swept in the three judges scorecards.
Aguirre fought courageously in the final stanza but was a beaten fighter when the last bell rang. His face was badly battered and bruised. Blood clogged up his nose and smeared his trunks. He had nothing to be ashamed of.
Neither fighter was ever in danger of falling down. Referee Tony Weeks had no difficulty working the bout which was highly competitive and clean from start to finish.
Hawkins and Ross scored it 116-112 and Trowbridge, 117-111, all for Viloria.
Peoples champion Manny Pacquiao, who was the commentator on Solar Sports live TV coverage at ringside, scored it 117-111 for Viloria.
In the dressing room after the fight, Viloria said he never took Aguirre lightly and knew he was in for a long night.
"I hurt my right hand in the third or fourth round when I hit him on the top of his head," said Viloria. "Hes got a very hard head. My hand just wasnt the same after that."
Vilorias right hand was swollen and packed in ice as he was mobbed by well-wishers in the dressing room.
"Aguirre came to fight and to win," said Viloria. "Give him credit. Hes a durable guy. I hit him with some good shots and he just wouldnt go down. Ill be a much better fighter after this. This was a learning experience for me."
Viloria dedicated the win to his mother Rosemarie who flew in from Honolulu the night before with daughter Roxanne and son Gaylord and his wife Doris and their 18-month-old boy Isiah. His mother celebrated her 49th birthday.
Vilorias father Benjamin said he was never worried during the fight. "I was confident Brian would pull through even if Aguirre was tougher than we expected," he said. "Look at him after the fight. He got beaten up. Hes lucky he survived."
Vilorias trainer Freddie Roach said on a scale of 1 to 10, he would rate the champions performance an 8.
"Theres still a lot to work on in the gym," said Roach. "I thought he lost his rhythm early going for a knockout with a single punch. He was a little slow, too. But he did what he had to do to win. Im proud of him. He adjusted well during the fight, moving to the body and bringing the fight to the middle of the ring."
Roach said Viloria tried to suck Aguirre in by using the rope-a-dope trick but never had the chance to land a knockout punch.
"That Aguirres a warrior," said Roach. "I knew he was a tough guy. Brian was stronger and smarter. It was a good test for him. He learned a lot of lessons in the fight. I think now Brian realizes you cant win every fight with an early knockout."
The win improved Vilorias record to 19-0 with 12 KOs. Aguirres record dropped to 33-5-1, with 20 KOs.
Aguirre conceded defeat but said he hopes his performance will give him another opportunity to fight for Top Rank promoter Bob Arum.
Aguirre, who was inactive for nearly a year due to injuries suffered in a motorcycle accident in 2001, said he was not given a chance to win at all by oddsmakers who picked Viloria to win by knockout. He proved them wrong by going the full route with Viloria.
In the press conference, Viloria thanked President Arroyo, Ilocos Sur Gov. Chavit Singson, Arum, his manager Gary Gittelsohn, his family and the Filipino people for their support. He also said he joins the country in mourning for those who died in a Southern Leyte landslide the other day.