For many Jamaicans, one of the most disturbing aspects of the burgeoning business of growing marijuana has been the rise of the Ethiopian Zion Coptic Church.

The church's sacrament is marijuana. Its spokesman are mostly white U.S. citizens. Its fianances are mysterious and its power on the island is growing daily.

According to Jamaican and U.S. officials, the Coptics, as members of the church are called, may be tied to 50 percent or more of the marijuana trade.

Late last year, Coptics were indicted in Florida for smuggling more than 100 tons of marijuana into the United States during the last several years.

According to the church's leading spolesman, Thomas F. Reilly Jr., known as Brother Louv, the Coptics own 10,000 acres of Jamaican land. Louv will not say how much, if any, of this is used for cultivating marijuana. lBut he is more than willing to praise the virtues of the herb, known as ganja here, with evanelical fervor.

"Ganja saved Jamaica from communism," Louv said recently, speaking over the telephone from his headquarters in a mansion on Miami's Star Island. "Who's going to save it tomorrow? The Drug Enforcement Administration? I doubt it. . . .

"If the DEA gives money to Jamaica, the people don't see that. We're trying to feed the people of Jamaica."

In fact, according to several well-traveled citizens of this troulbed nation, the Coptics have gained considerable popularity among the rural poor by taking over fallow land, building high-quality paved roads -- which can easily double as landing strips -- and importing fertilizer and sophisticated farming techniques to improve it, considerably increasing the accessibility and productivity of entire regions of the country. i

But others, like Dawn Ritch, a columnist for Kingston's Daily Gleaner newspaper, regard the Coptics with deep suspicion. After visiting the main Coptic farm in St. Thomas, about 30 minutes from Kingston, Ritch wrote, "This was the closest experience I've ever had to what the atmosphere might have been at Jim Jones' Peoples Temple." He was referring to a religious cult in Guyana, made up mostly of Americans, that committed mass suicide. Since the church first became visible in Jamaica and Miami during the mid 1970s, it has been almost constantly involved in litigation with the Florida and U.S. governments.

Brother Louv dismisses the several civil and criminal cases brought against his church as the result of hysterical, unfounded prejudices against marijuana and of government persecution.

In many ways a product of the 1960s, Louv, 37, talks of the need to give back to black people "what our fathers stole." Louv was born an Irish Catholic in Massachusetts.

When he was 25, Louv said, he was the vice president of a small computer serivce firm in Framingham, Mass.

"Then I had my first smoke and two years later I discovered the Coptic Church," he said.

Louv's current faith has nothing to do with the Coptic Church of contemporary Ethiopia and Egypt. Neither does it have any doctrinal link to the Rastafarian faith in Jamaica, which also involves a good deal of sanctified marijuana smoking.

Rather, Louv said, it is a separate religion growing up in Jamaica from African roots that recognizes the spiritual identity of God and man. The marijuana smoking, he went on, is called for by various verses in Genesis and Exodus dealing with sacred herbs and the burning bush.

None of this has held much weight with the U.S. courts, which thus far have refused to allow the Coptics to use marijuana legally as a part of their religious services.

Meanwhile, the church has branched into a variety of enterprises, including the magazine Coptic Times (which claims a circulation of 25,000) and in Jamaica the Coptic Container company, which owns several trucks and does contract hauling on a large scale. The church also reportedly owns one of Kingston's major supermarkets.

Few Jamaicans failed to note that at a time when most businesses were desperately short of inventory and capital goods, the Coptics were able to import heavy road-grading and farming macninery, and the shelves of their supermarket were the best stocked in town.

"What they have in mind we don't know," said Jamaican Prime Minister Edward Seaga earlier this week, "but obviously we will have to look at the whole structure of their organization to see just what its antecedents are, who's behind it and what its plans and proposals are."

Louv offers this long-range vision for Jamaica, troubled by violence and poverty: "The people are going to look for something nonpolitical to put their faith in. They're going to see the ganja man and he's going to lead them to the Pearly Gates."