Dera Tompkins hesitates to discuss her faith. People misunderstand.

Tompkins is a 35-year-old medical librarian who lives in Northwest Washington. She is also a Rastafarian.

Rastafarianism is a Jamaican-born religion that combines Bible study and a belief in natural living with the loping rhythms of reggae and the "enlightening" properties of marijuana. "Jah" is the supreme being. Haile Selassie, the late Ethiopian emperor, was the "living God." Bob Marley, the supple-voiced singer who died in 1981, was its messianic figure, folk hero and rock star.

But Rastafarianism, which has an estimated 500 followers in the Washington area, is a religion and a life style that invites two very different perceptions. Tompkins describes the true Rastafarian as "a peace-loving humanitarian," upright, artistic, intensely private.

However, police say that Rastafarians are often violent criminals engaged in drug trafficking and drug wars. In preparing for "Operation Caribbean Cruise," an ill-fated predawn raid yesterday that netted far fewer arrests than expected, the D.C. police department described its targeted group of area Rastafarians as "members of a religious cult."

"They have organized themselves for the purpose of distributing narcotics . . . " the department said in an "operational handbook" on the raid. "They are a well-connected group, separated from the rest of society by their religious zealousness and their love of marijuana."

Area Rastafarians who were not involved in the raid said yesterday that their culture, like any group, has good and bad elements. There are also many "pseudo-Rastafarians," they said, who effect some features of the faith while merely pretending to be sincere followers.

But they also spoke of the stigma that accompanies their beliefs and makes them a target of discrimination and police surveillance.

"Nobody takes the time to understand us," said a 32-year-old Jamaican native who lives in Adams-Morgan. "Nobody gives our look a second chance."

To outsiders, the most striking features of Rastas are their appearance and their use of marijuana, or ganja, as a sacred rite. Most wear their hair in ropy strands called dreadlocks. They often wear red, green and gold, the colors of the Ethiopian flag. Marijuana is smoked in large, fat, cigarettes called "spliffs," or in water pipes called "chillums."

"We believe the marijuana plant is the tree of knowledge and understanding given to humans by God," said the Adams-Morgan resident, who did not want to be identified. "It is a healing herb."

The Rastafarian movement began in the early 1930s. It was based on the prophesies of Marcus Garvey, a Jamaican native and back-to-Africa advocate who built the largest black organization in American history during the pre-Depression years, the Universal Negro Improvement Association.

As a religion, it is largely an individual concept; there are no organized churches, although Rastas sometimes gather for Bible study.

In Jamaica, Rastafarianism found favor in the ghettos, where the white society was viewed not only as oppressive but also one that rejected African culture and the dignity of the black individual. The Rastafarian population is estimated at 70,000 on the island.

The culture was spread to the United States by Jamaican immigrants and embraced by American-born blacks, like Tompkins, who "found a true black identity" with Rastafarianism. "I'm very proud of what I am," she said yesterday. "I'm an African born in America."

But the religious aspect of the culture is equally important, she said.

" 'Rasta' is a very high concept," she said. "It means 'righteous.' We are supposed to be a bright shining example, a very positive thing.

"But because our religion is anti-establishment," she continued, "it is given a bad rap. And when one Rasta does something, the whole group is held responsible."