Catholic Boy's schools here had no Christmas trees this year.

The catholic mission celebrated a Christmas mass for a tiny handful of parishioners.

The eggnog was served alcohol-free.

It was the first Christmas in the Islamic Republic of Iran, a day of mixed feelings for many members of Tehran's dwindling Christian population.

Although the newly approved constitution assures Iran's minorities religious freedom, the strong Islamic cast of the now government creates a feeling of isolation and self-consciousness for many non-Moslems.

"It was very peaceful before the revolution." said a local clergyman who asked to remain anonymous. "Now there's a lot of confusion. You just don't know what turns this revolution might take.

"Christians in Moslem countries -- sometimes there are massacres in the name of Allah."

For Father Augustine Valkenburg, a Priest at St. Abraham Catholic Church and a leader of the 12,000 Catholics here, this Christmas is an improvement over last year's, when revolutionary street fighting prevented him from holding a midnight mass.

"At least you feel you are safe this year," he said.

IRAN'S CHRISTIAN population has declined steadily since the revolution last February. Although no precise figures are available, most local clergymen estimate that more than 200,000 Christian remain today -- the vast majority being Armenians.

For those celebrating Christmas yesterday -- the Armenian Christmas is Jan. 6 -- the City of Tehran offers none of the winter festiveness of American cities with their colorful street decorations, full evergreen trees, carolers and window displays. This was just a normal work day in Iran's capital.

The Armenian section of town comes closet to having some Christmas spirit. Florists with "Merry Christmas and a Happy New Year" signs in their window do a brisk business in poinsettias while other shops stay well stocked with artificial Christmas trees, lights, ornaments and, of course, toys.

A LARGE SANTA CLAUS marks the entrance of the Baba Noel shop in central Tehran, where the shelves are lined with plastic Walt Disney characters, replicas of the Boeing 727 and G.I. Joe "Man of Action" models, (a strange gift in view of the daily government denunciation of American imperialism).

"We sell 30 times more Barbie dolls than G.I. Joes," remarked the 25-year-old shop owner, Hamid Fathi.

The occupation of the U.S. Embassy here and the taking of 50 American hostages dampened the Christmas joy for some celebrants.

"People have not felt the spirit of Christmas as much this year because of the hostages," said a Tehran clergyman. "It's a kind of solidarity with the people who are suffering unnecessarily."

Some of the parishioners at the Catholic mission in north Tehran said they offered prayers for the hostages during Christmas mass today. Only 12 people attended the service, which was held in a simple chapel decorated with a Christmas tree and balls of bright ornaments.

"The church used to be full on a day like this," said one parishioner. "There'd be parties and festivities, plenty of wine to drink. Its awful quiet today."