STEELE, Mo. — At the beginning of an evening worship service at the First Assembly of God church, the Rev. Ryan Harris pitted teens against adults in a trivia game called Battle of the Generations.

After a few more games, worship began in a style typical of evangelical churches.

Harris, a husky 26-year-old wearing a sweater, untucked shirt and baggy jeans, led 20 teenagers and 20 adults in a few upbeat, contemporary praise songs, and then delivered the night's message.

"The gift of the Holy Spirit is placed upon you, it's placed inside you," Harris told his congregation, his voice thundering through his headset to the back walls of the tiny church. "The Holy Spirit gives you strength to stand up to those who don't want you to stay in school, who want you to try drugs, to try sex."

It's the Holy Spirit that provides Pentecostals with the practice that sets their movement apart from all other evangelical Christian churches: speaking in tongues, or glossolalia.

"The distinguishing feature of classical Pentecostalism is to say that unless you have spoken in tongues, you don't have this baptism in spirit," said Russell Spittler, emeritus professor of New Testament at Fuller Theological Seminary in California.

The practice is so central to the 3 million-member, Missouri-based Assemblies of God, that denominational leaders voted unanimously to reaffirm it as doctrine during the church's General Council meeting in

Reaffirmation of one of Pentecostalism's central tenets was necessary, according to the resolution voted on at the meeting, because speaking in tongues "has come under certain scrutiny."

Glossolalia has become the church's real battle of the generations. Some young pastors say that while they recognize the foundational importance of speaking in tongues to Pentecostalism, other features of their faith are more practical and helpful for their flocks.

Harris, who began preaching when he was 12, and he said audible glossolalia is heard just "once every two or three months" at the church.

"We do stress that the initial physical evidence of the Holy Spirit is speaking in tongues," Harris said. "But we do not encourage people to seek tongues. We encourage them to seek God and to seek the power of the Holy Spirit for witnessing. Tongues is just a byproduct of that."

Sentiments like that worry an older generation of Assemblies of God pastors.

"There's concern from our leadership that younger pastors are possibly taking their cues from other significant Christian movements like the emergent churches or user-friendly churches," said the Rev. Boyd Brooks, 57, pastor of The People's Church, an Assemblies of God congregation in Arnold, Mo. "It's a legitimate concern that these churches are not being fully Pentecostal."

Brooks said one might hear someone speaking in tongues once a month in his church — "Not as often as I would like," he said.

Pentecostalism is distinguished from other evangelical movements by its emphasis on Scripturally-based "gifts of the spirit," including healing, prophecy and speaking in tongues.

The movement began at a street revival in Los Angeles in 1906, but was marginalized by more mainstream Christians for much of the 20th century because of its emphasis on gifts of the spirit.

"Initial physical evidence is the key issue, and numerous Assemblies of God ministers are no longer tied to that doctrine," said Stanley Burgess, a professor of Christian history at Regent University in Virginia, and editor of "The New International Dictionary of Pentecostal and Charismatic Movements." "Younger pastors are no longer nearly as committed to this as their elders are."

But George Wood, general superintendent of the Assemblies of God, downplayed the importance of the general council's reaffirmation of the church's doctrine this summer.

"The fact that it passed unanimously suggests that the concern was overstated," Wood said. "There's always the case that my generation is going to be concerned about the handoff to a new generation. It's easy for a denomination to stray from its moorings, and that's an honest concern, but in this case, I don't think statistics back up that concern."

The Rev. Paul Scheperle, 37, pastor of First Assembly of God in Washington, Mo., said the issue is more about differing congregational dynamics than generational differences.

"Individual pastors at individual churches are just responding to the receptivity of their audiences and their particular needs," Scheperle said.