YONKERS (By Jennifer Medina, NYTimes) December 24, 2006 and December 16, 2007 — Crowded almost shoulder to shoulder in a bare one-bedroom apartment, the women and children nibble on tamales and sip hot chocolate, bracing for the bitter cold outside. Soon, they will begin their nightly walk.

They will march down South Broadway and begin la posada, Spanish for "the inn," re-enacting the biblical story of Mary's and Joseph's search for a room in Bethlehem the night before Jesus was born. As the 30 or so members of the extended Aguilar family begin their procession to a home a few blocks away, they are carrying on a tradition that has endured for hundreds of years, thousands of miles away in their Mexican homeland.

"In the name of heaven, can you give us shelter?" they sing in Spanish, arriving outside the door to an aunt's apartment. "Because my beloved wife cannot travel."

A chorus of voices from inside responds: "This is not an inn, move on. I cannot open it, I don't know if you are some kind of criminal."

The back and forth continues, until after pleading for six more verses, the group is finally allowed in.

Many historians believe the tradition of Posadas in Mexico dates back to missionaries in the 16th century, who were trying to teach indigenous people the story of Christmas. Other Latin American countries have adopted similar traditions, with entire villages taking part in processions during the nights leading up to Christmas Eve.

Here, though, the processions take on different meanings, as immigrant families struggle to keep the tradition alive. Many can see their own personal history reflected in the biblical story, said the Rev. John O. Grange, the pastor at the Church of St. Jerome in the Mott Haven neighborhood of the Bronx, where about 80 percent of its 1,000 members are Mexican.

"They see that the holy family was shut out, and they have that same kind of experience," Father Grange said. "They come here looking for a home and they are shut out. Even if that is not the way they explain it to their children, that is the reality. And they see that eventually the families find a home."

For Lus Maria Aguilar, who is known as la dueña, the boss, of the family, there is one reason she spends hours coordinating the monthlong festivities in south Yonkers.

"They have to keep doing it," said Ms. Aguilar, motioning to the dozens of children in the room on Monday night this week. "They have to keep the customs of our country. Now we are here and they go to school and learn that Christmas is about presents. But this tells them no, it is about God."

To keep the Posadas going, there are compromises that must be made. House-to-house processions are common in California, Arizona or Texas, but many immigrant families find it difficult to do the same in New York, where people typically live in small apartments. Some parishes, like St. Jerome's in the Bronx, have tweaked the tradition, with people knocking on the doors of the church to perform the Posadas.

Rosie Garcia, who is part of the Aguilar family, recalls the Posadas back home as being quite different. In the small central Mexican town of Tehuitzingo, where she grew up, the processions would clog the streets, with music blasting from homes and children playing with piñatas late into the night.

"Of course it is not the same here," she said, holding her plate of steaming tamales wrapped in corn husks. "But in my heart, I wouldn't know that it is Christmas without this."

Typically, Posadas are held for the nine nights leading up to Christmas Eve, but the Aguilar family's tradition has expanded to the entire month, to allow more people to participate.

"It is an honor to have this at my home," said Guillermina Lopez, who was the host at Monday night's posada. Like the women who had been hosts before her, she had set up an elaborate altar to hold the manger. Dozens of candles crowded a table and a Mexican flag hung on the wall surrounded by sparkling Christmas decorations.

"We make everything ourselves so that the others can celebrate," Ms. Lopez said.

Each night, the Aguilar family begins at the same home where they were the previous night. Before they leave, they offer prayers for the host, asking that God bless the home that allowed them in. As they sing "God is with me" while walking past homes, pizza shops and hair salons, a few people come to the window to watch the passers-by.

"Can I come?" one teenager shouts out.

The young Aguilar cousins often explain the Posadas to friends at school and occasionally recruit them to join the family for a few nights. One cousin, Jenny Balbuena, 6, proudly announced to a visitor that she had not missed a single night.

"I know all of the songs by heart," she said, watching the red wax from her candle drip on her powder blue glove. "Isn't it pretty?"

There is no room in the apartments for piñatas, so the parents usually pass out small bags filled with treats of chocolate, peanuts and lollipops. Bags of Doritos seem to be the most popular contemporary addition.

The most exciting time will come on Friday night, when the children will dress as Mary, Joseph and the three kings. All the parents have the night off, so the group, both Aguilar family members and friends, may swell to 100 people. They will sing, dance and eat more tamales.

And, at last, they will break a piñata.