"The best thing about it was seeing the children smile ear to ear," said 13-year-old missionary Joshua Hester of the Les Cheneaux Christian Fellowship Church, who recently completed his first trip to Tijuana, Mexico. There, he worked with a fellow church member, 21- year-old David Kasper in Mexico's westernmost city, in the state called Baja California, from July 26 through August 2. They helped build new houses, restore old ones, and told religious stories and played games with local youth.

The effort was under the auspices of Global Expeditions, a missionary program overseen by Teen Mania Ministries, and involved 800 missionaries from several states. Mexico has pledged to help with traveling expenses and materials next year, if the group returns.

Missionary work brings hope to the poverty stricken area, said Mr. Kasper, who returned to Baja California after volunteering near Tijuana in 2007.

"Both boys wanted to serve people and help people in need," said Joshua's mother, Davine Hester, whose husband, Scout, is pastor of Les Cheneaux Fellowship Church.

Mrs. Hester has served as a missionary in several countries and helps youth get involved in similar work.

The boys shared Christian thought through direct conversations at people's homes, through their building work, by taking part in religious dramas, and by telling stories to children on the streets of the city, she said.

"It is definitely evangelism," she said. "They went there to get people into Jesus Christ."

It is an area that appreciates assistance, she said, citing earthquakes and hurricanes that have devastated Mexican communities and left many homeless.

The boys took very little with them. Their suitcases were packed with toys for children.

"It's amazing," Mr. Kasper said. "When we were pulling in, seeing how they live, it just makes you want to give away everything."

Mr. Hester said Tijuana appeared "beaten down," although the backdrop of hills is a pleasing sight, he added.

Last year, working on mountainsides outside of Tijuana, Mr. Kasper saw dwellings made of car doors and pieces of scrap wood, built on land the people there did not own. They were constructed near power lines, which people tapped into using jumper cables, he said.

Last year, he helped build a house in the rural area.

"This year, I really wanted to spend time with kids," he said.

In Tijuana, both he and Mr. Hester had the chance to do so every day.

In the morning, they helped build and repair houses. In the afternoon, they took part in a Vacation Bible School program, in which small groups, overseen by one man and one woman from Teen Mania, fanned out over Tijuana and asked youngsters to take part in games, stories, and watch Biblical dramas.

"By the end of the week, we had around 60 or 70 kids," Mr. Hester said, speaking of his own Bible school group. Translators helped the missionaries convey stories to the children.

"They liked the stories." Sometimes they asked questions about them. "One of the kids asked if we could stay another week," Mr. Hester added.

"The group tried to show that there are people who care about them," Mr. Kasper said. "We tried to touch the lives of the people down there. They have it so hard."

Organizers even had to intervene in a serious family conflict that involved a boy who obtained a knife to kill another child, simply because their families did not get along, he said.

There were several satisfying aspects to the trip. One of the most powerful was "to see the look on someone's face after we made them a home," Mr. Hester said.

When his group went out in the morning, they were directed by organizers to work at certain homes, where contractors would explain what they were to do. Some days, he helped put frames up. Others, he worked on drywall, and they talked to the home owners about Christianity at their homes.

"They were really happy" and thanked the missionaries for their efforts, he said.

Mr. Kasper, who has building experience, worked with a team that constructed a new house for a woman named Elma. Inside, the group filled the walls with lines of scripture, and prayed with her, he said.

Often, groups had extra paint or materials, so they walked the streets offering to paint gates, walls, and to do other maintenance work.

Mr. Kasper was struck by the expressions on peoples' faces when he offered to paint something that had never been painted before, things the owners could not afford to paint, he explained.

"It was an awesome opportunity to talk to them," he added.

It was during this restoration work that a Mexican politician in the area met with a Teen Mania organizer to learn more about the group. He then pledged to pay half of the group's traveling expenses and materials, if they return next year and spend two weeks, Mr. Kasper said.

Mr. Kasper will return to Tijuana next year, or go on a missionary trip to Madagascar, an island nation in the Indian Ocean.

Both missionaries said they were particularly fond of the children they met, and they agreed that the most challenging part of what they did was to leave them behind.