Ronaldo told Brazil's parliament yesterday he insisted on playing the 1998 World Cup final because he felt well and medical tests were normal.
The 1996 and 1997 FIFA world player of the year had convulsions hours before their 3-0 defeat against France at the Stade de France in Paris on July 12th.
Ronaldo, speaking on the first day of his testimony before the parliamentary commission (CPI) which is investigating irregularities in Brazilian football, said: "After medical tests were clear and I felt well, I insisted on playing the final."
He added: "It was the saddest day of my life, because of the defeat, but I overcame the episode. If I had to do it again, knowing what happened, I would play again."
The CPI are also investigating tax evasion by players, Nike's contract with the national side, and the sale of young players to foreign clubs, allegedly with false passports.
Brazilian MPs are concerned that Nike potentially has too much influence on the national side's schedule - and they had feared that the company might have pushed for the inclusion of Ronaldo even though he was not fully fit.
The controversial 10-year, $160 million Nike deal was signed in 1997. The American manufacturer has exclusive rights on all marketing aspects and can organise 50 friendly internationals, with a minimum of three per year, in which at least eight players of the first-choice side must play.
Referring to the Nike deal, the Inter Milan player said: "The contract with Nike is an international contract and has a secrecy clause and unfortunately I can't say anything about it."
Ronaldo did say that the contract was "for life, like many contracts by athletes sponsored by Nike."
But he said: "The only agreement I have with Nike is to wear their brand of footwear. It's the only thing that Nike have requested of me until now. "I'm not here to defend Nike or the Brazilian Football Confederation but I have no doubt that Nike are serious."
And he said that faced with the constant probing he would not be surprised if the sportswear giants withdrew from Brazil.
"With all the investments that Nike have made in Brazilian football and faced with all these questions, if I were Nike, I'd pull out of Brazil," added Ronaldo.
Romario, Brazil's star player in their 1994 World Cup win, is also set to come before the CPI. The striker is suspected of not paying taxes while playing at Barcelona.
He is believed to have transferred money back to Brazil but did not declare it to the fiscal authorities.
Other players yet to come before the CPI include 1994 World Cup winning captain Dunga, Caesar Sampaio and Real Madrid free-kick specialist Roberto Carlos.
The CPI has already spoken to former Brazil coach Mario Zagallo, ex-FIFA president Joao Havelange, team doctors and other Brazilian internationals.
