Ronaldo underwent medical tests for AC Milan on Friday following the Italian club's offer to Real Madrid for the Brazilian star.
Ronaldo underwent tests at a private clinic near Como. He then at lunch with coach Carlo Ancelotti before further tests at the club's training center in Milanello. He later returned to Madrid on a private jet, the news agency ANSA reported.
Milan has made an undisclosed offer for the 30-year-old striker and club vice president Adriano Galliani has said he will travel to Madrid on Monday in the hope of completing the signing.
Ronaldo left the Spanish capital by private jet on Thursday to attend Milan's 2-2 draw with AS Roma in the first leg of an Italian Cup semifinal at San Siro stadium.
"After the game Ronaldo came to greet us, he seemed very happy," Brazil midfielder Kaka said Friday. "He chose Milan over another offer that was financially more substantial."
Kaka, who plays with Ronaldo for Brazil, said teaming up at Milan would be "a dream come true."
Italian sports daily Gazzetta dello Sport said the deal had not been sealed yet, with Milan offering euro7 million (US$9 million) for the player and Madrid asking euro7.5 (US$9.7 million).
Much will depend on the results of the medical tests, the paper said.
"It's not yet all over," Ronaldo was quoted as saying by news agency ANSA.
Ronaldo has six days remaining in the January transfer window to switch clubs. Otherwise, he will have to stay at Madrid at least until the end of the season.
The forward, who hasn't been picked for Madrid since the Jan. 7 defeat at Deportivo La Coruna, said on Monday his difficulties with coach Fabio Capello seem set to force him out of the club.
A move to Milan would take Ronaldo back to the city where he spent five years with rival Inter Milan. He joined Madrid in 2002, winning the Spanish league at the end of his first season _ his last major title.