SAN FRANCISCO - They climb mountains on a quest for a vision. They beat drums and shake rattles. They pray in sweat lodges. Some study for years and later teach others the spirituality they paid to learn.

They are a growing population. But they are not Native. And as self-proclaimed medicine men and women or shaman - referred to by some critics as ;'plastic medicine men'' or ''shake and bake shaman'' - they often charge for spiritual services.

That, for many Natives here, is a big problem.

''Even if they're not charging for money, they have no idea about our people's ways, they have no idea what they're doing and how catastrophic it can be,'' said Jimmy Red Elk, 32, a traditional Oglala Lakota who lives in Los Angeles. ''It's really bad out here.''

The liberal-leaning state has always been abundant with New Age centers and people who advertise Native-themed services ranging from ''Native healing and ceremonies'' to ''pilgrimages to sacred places.''

Over the past two decades, such centers and retreats run by non-Natives have spread across the state - and the country - sometimes with deadly results. In 2002, two people died after spending more than an hour in a sweat lodge in southern California run by the group the Shamanic Fellowship.

Traditional elders, activists and groups have written resolutions and held protests denouncing such services. Some have even forcibly shut down questionable practitioners by dissembling their sweat lodges.

But such practices have only increased. And, in recent years, even more groups have sprouted up online.

''Our ways are not for sale!'' wrote D'Shane Barnett, 31, a member of the Mandan and Arikara tribes, in an e-mail sent recently to dozens. ''People cannot claim to understand our ways with one breath and then offer to sell them with their next breath.''

Barnett, a special projects officer at the Native American Health Center in Oakland, was referring to an e-mail he received by mistake, intended for a company called Native American Nutritionals. From their site he had been lead to another, thenativehealer.com.

There, he found an offer of ''spiritual adoption'' for a $90 donation and $5 in monthly payments by the Nemenhah Band and Native American Traditional Organization of the Oklevueha Native American Church of Sanpete.

The group is an ''independent band'' which offers enrollment in an online college where people can pay to qualify as medicine men or women, healers and Native practitioners, according to their Web site.

Courses range from online lessons in smudging to a six-hour ''Unipi Ceremony Practicum,'' which requires a mentor to ''come to your lodge.''

Each member receives a ''ministerial card'' that is valid as long as they are progressing and ''making regular offerings,'' according to the Web site.

Similar Native-themed services are offered for a price across the country. In Washington, Tana ''Blue Deer Woman'' Hamiter offers vision quests for $300 on www.onwingsofflight.com. A ''Southwest Spirit Quest Tour'' offered by www.divine lightministries.com includes ''a night spent in a traditional Navajo hogan'' and ''authentic Native ceremonies.''

''My first reaction was anger,'' Barnett said. ''But when I spoke with a couple of different medicine people, the way they explained it to me is that I need to pity these people. What they are doing is filling a void.''

Though it may not appear so, seekers of Native spirituality are often well-intentioned, said Ann Riley, a shamanic counselor in the East Bay.

''The yearning for a spiritual connection is common,'' said Riley, 70. ''Americans are very drawn to the Native American spirituality because it's the indigenous spiritually of this continent.''

Riley is a white, retired schoolteacher who for 15 years has studied ''shamanism'' - which she defines as a technique for connecting with ''spirits for healing and problem solving'' - with a shamanic center in Marin.

Today, she charges $75 for a 1 and 1/2 - 2 hour session, during which she uses a drum or rattle to help students ''enter an altered state'' from which they connect with spirits, she said. It usually takes four to five lessons, she explained.

At her El Cerrito office she holds drumming circles and long-distance group healing. Her students include teenagers and ''lots of psychologists,'' she said.

She has known self-proclaimed spiritual leaders who have gotten sick by taking hallucinogenic drugs from South America or Mexico in ceremony.

''Sometimes white Americans go to some other culture or read about something and think they know how to do it,'' she said. ''It's really something that you have to immerse yourself in. I see it really as lack of respect.''

Philip Scott, 44, said he has immersed himself in ''the Native Path for more than 25 years,'' in an ad in the New Age magazine Open Exchange.

Today, the founder of the Ancestral Voice - Center for Indigenous Lifeways in Novato, he offers services including ''Rites of Passage'' ceremonies and classes in ''Native drum and flute.''

Scott said he is of European and Cherokee ancestry, though he isn't sure how much. And, he is Lakota not ''by blood ancestry, but by affiliation,'' he said. After years of studying various spiritual practices, he had a dream about the Sun Dance, he said. He received permission to dance in South Dakota, he explained.

''During my third Sun Dance, the spirits came to me and said I need to create a center,'' he said. Scott said he was ''bonneted'' at a Texas Sun Dance as a ceremonial leader.

Today, Scott holds Sweatlodge ceremonies - some of which have included newborn babies, he said - and doctoring, birthing and death ceremonies in the Lakota tradition. He has taught ''warriorship practices'' to youth and has worked as a Native spiritual adviser at the Napa State Hospital in Marin.

And he takes people on vision quests. ''I help people learn how to be human, responsible stewards of the Earth,'' he said. ''I listen to the directions the ancestors give me.''

Scott is earnest, saying he rarely receives criticism, and that people's doubts quickly dissipate when they see him in action.

''There is a lot of appropriation of Native practices and tradition,'' he said. ''There has to be that level of intent and experience that you bring. In time, the spirits will make clear who is legitimate and who is not.''