Twenty years after the 1994 original, Dumb And Dumber To has opened with 38.1 million dollars (£24.3 million) at the US weekend box office, according to studio estimates.
The Universal sequel debuted almost exactly two decades after the Farrelly brothers first introduced the Jim Carrey and Jeff Daniels low-IQ duo.
Dumb And Dumber To edged out the animated Disney adventure Big Hero 6, which took in 36 million dollars (£23 million) in its second week.
Christopher Nolan's sci-fi epic Interstellar slid to third in its second week with an estimated 29.2 million dollars (£18.6 million). The film continues to blast off overseas, where it took in 106 million dollars (£67.8 million) over the weekend, with sales particularly boosted by a strong opening in China.
The top three films took up the lion's share of the box office, with the number four film, the romance Beyond The Lights, opening with a distant 6.5 million dollars (£4.1 million).
In a Hollywood constantly updating old properties, Dumb And Dumber To was still unique. In between instalments, there was also a 2003 prequel, though it was made with different actors and wasn't directed by Bobby and Peter Farrelly.
"This was a gamble," said Paul Dergarabedian, senior media analyst for box-office tracker Rentrak. "Cinematic history is littered with long-lead sequels that just haven't worked."
"It's always a risky move to wait this long, but in this case, the casting of Jim Carrey and Jeff Daniels really made a difference," he added.