Thirty-one former American hostages, their once gaunt faces transformed by good food and family reunions, arrived today at the antebellum Greenbrier Hotel here for three days of psychological evaluation and relaxation.

This reunion in the rolling spring-green hills of West Virginia at one of the nation's most gracious -- and expensive -- resort hotels could well be the last one for the hostages, who along with 20 others spent 444 days together as captives in Iran until their release almost exactly three months ago. But that depends on whether State Department assessments are borne out that most have suffered no long-term harm from their capitivity.

But while the hostages geared up for the series of meetings with 20 psychologists and psychiatrists and up to six days of an all-expenses-paid vacation, courtesy of the Greenbrier, State Department officials were privately expressing some anger over the refusal of any of the nine Marine Corps ex-hostages to attend.

Their vexation stems from Marine Corps press statements earlier this month that one State Department official said implied that the Foreign Service officials who were held hostage were not as "tough" as the Marines.

None of the Marines were held in closets," said a State Department official. "They were able to associate with each other more than the others. The difference in treatment between the Marine guards and the others is a significant factor in how they have responded since their release."

A Marine spokesman said today that "I think you have to look at the training the Marine security guards underwent. All went through Parris Island or boot camp in San Diego. That prepares them for rigors and stress. Their backgrounds are a little different from the backgrounds of the other hostages. They have the spirit, pride, and esprit de corps of being Marines."

The spokesman said that all "the Marines have resumed or will-resume this weekend new duty assignments and consequently will not attend." Their examinations in Wiesbaden, West Germany, after their release showed all to be in excellent health, physically and mentally, he said.

For the 31 ex-hostages -- now called returnees by the State Department -- the next three days will include a series of large general meetings, at which doctors will explain what they hope to find, coupled with smaller group meetings.

The hostages will be split into small groups of four or five, State Department spokesman David Nall said. Two or three doctors will join the group for discussions. At the same time, family members will participate in slightly larger group discussions with doctors and several family counselors who worked with the hostage families during the period of captivity.

Nall said the overall objective is to see how the hostages are readjusting to their families, wives and work while also gaining some insight into the problems of those held in captivity for future reference.

Despite the presence of almost 80 reporters and television cameramen, the entire session is to be held behind closed doors. Whether any of the doctors will discuss the evaluation publicly is yet to be decided, Nall said.

The only hostage family that consented to meet with the press today was Moorehead C. Kennedy, the Tehran embassy economic and commercial officer, and his wife, Louisa, who was one of the leaders of a group that represented the families during the period of captivity.

"I think we're going to be meeting here really for the last time as a group," said Kennedy. "We're here for a nice time and a rest."

Louisa Kennedy said that the hostages and their families had drafted a congratulatory telegram to be sent to the space shuttle pilots after their successful landing today.

"Actually we don't know what the thrust is of this meeting," she said.