FALL RIVER, Mass. (AP) _ John Huston's condition remained serious but stable Thursday, two days after the Oscar-winning director was hospitalized following a bout with emphysema, a hospital spokeswoman said.

''The family has said that they're very encouraged. He's comfortable,'' said Dorothy Allen, spokeswoman for Charlton Memorial Hospital.

Huston, who marks his 81st birthday Wednesday, was stricken Tuesday just before he was to go before the camera in Newport, R.I. He was to play the part of an eccentric millionaire in ''Mr. North,'' a film comedy being shot in the posh playground of Newport.

Robert Mitchum stepped into the role Thursday.

Ernie Anderson, publicist for the film, said Huston's family and friends believe he will recover.

''He's a really tough old hide. It may be a week or 10 days or two weeks, but he'll be out of this,'' he said. When Huston was laid up with emphysema in April he wrote 20 pages of the screenplay for the flim.

Huston spoke with his children, Danny and Anjelica, Wednesday, and was encouraged by the fact they they are continuing to work on the film, Anderson said.

The $5.5 million production is a family project. Huston was a co-author of the film based on Thornton Wilder's ''Theophilus North''; his son, Danny, is director, and his daughter, Anjelica, is performing in a leading role.