Eileen Chao works with people who, for any number of reasons, are less than comfortable with sex.

Some of her clients are adult virgins who have severe anxiety about performance and vulnerability; others have recently undergone a gender transition and are looking for help getting accustomed to their new bodies. She also works with people whose religious upbringing has complicated their relationship with sex or taught them “that their body is not to be trusted.”

Ms. Chao is a surrogate partner in San Francisco. Unlike in more traditional forms of therapy, in which practitioners are usually careful to keep clients at arm’s length, a surrogate partner “enters into a temporary relationship” with a client on an intimate level, she said.

“It’s really for clients to learn relationship skills and also develop a relationship with their own sexual selves,” she said.

Ms. Chao, 42, described her office as a “relationship laboratory” in which she initiates different experiments to help clients identify whatever their barriers to emotional and physical intimacy might be.

One of the first things she does with people is help them engage in their breath. What do they notice as they take deep breaths? What changes do they notice in their bodies? They also experiment with touch, taking turns and focusing on what it feels like to receive and give.

Ms. Chao, who also works as a sexual intimacy coach — a similar job, though clothes stay on — believes the exercise helps clients get out of their heads, where thoughts like “Is my partner bored?” or “Am I doing this right?” can be difficult to ignore. The goal is to return to their bodies.

Surrogate partner therapy typically begins with a referral from a talk therapist, who first evaluates whether someone is a good candidate for this kind of treatment. Sessions are typically held weekly, in one- to two-hour meetings until all three agree that the therapy is complete. It’s not typically covered by insurance, and, although fees vary, it can range from $75 to $350 an hour.

Surrogate partner therapy was originally conceived in St. Louis in the 1960s by William H. Masters and Virginia E. Johnson, pioneers in the research and understanding of human sexuality.

According to Andrew Heartman, a co-founder of the Surrogate Partner Collective, the concept of surrogate partner therapy was introduced to the public in 1970 with the release of Masters and Johnson’s book “Human Sexual Inadequacy.”

“They were all very oriented toward sexual dysfunction,” he said of Masters and Johnson. “Consequently, they measured success by the couple being able to engage in the heterosexual intercourse.”

Surrogate partner therapy today tries to go beyond that approach by being L.G.B.T.Q.-affirming and more diverse.

“Instead of viewing it as treatment for sexual dysfunction with the goal to be intercourse, now the intention is to help people have better relationships and better relationship skills,” Mr. Heartman said.

“Sexuality can be included in that because sex might be a part of relationships, but ultimately, it’s a much larger umbrella than originally conceived,” he added.

Mr. Heartman, who has been practicing for 13 years, mostly works with cisgender and transgender women, nonbinary individuals and people with disabilities. He doesn’t work with male clients, gay or straight, because he is not attracted to men.

Because of the nature of the job, he said, it would be better for a male client “to be with someone who’s going to respond to him, like someone who might respond to him with actual attraction.”

In interviews, surrogate partners explained the many misconceptions surrounding their profession. Surrogate partners are not prostitutes, for starters. Many practitioners also object to being called sex surrogates, because they believe their form of therapy is about much more than sex.

For example, Ms. Chao, who has been doing this for about 10 years and is also a member and instructor in the Surrogate Partner Collective, frequently works with clients to figure out their unique relationship needs, but she personally doesn’t engage in sexual activities with clients.

She has also had men come to her just looking for sex.

“A lot of them say things like, ‘Oh, I don’t want to do this work with someone who’s forced into doing this or someone who’s been trafficked,’” she said. “And there’s also a lot shame around being a client of sex work, so I do a lot of education around that, too.”

Nicole Ananda, a 48-year-old surrogate partner near Philadelphia and another co-founder of the Surrogate Partner Collective, said that the biggest misunderstanding about this job is the assumption that because it involves sex, it’s all about sex.

“Even though we center on someone’s sexuality and their lack of sexual energy, it really is all about relationships and helping people connect with themselves,” she said in a phone interview.

In the past, she has met with resistance when trying to find somewhere to practice. In an interview, she said that once, when she was trying to buy a condo, she was denied use and occupancy permits over suspicions about her practice.

“I didn’t pursue it legally because it’s just not worth it,” she said. “They told the condo board at the place we were trying to buy an office space that we’re doing something illegal and they shouldn’t sell it to us. And so they killed the deal.”

Ms. Ananda’s practice, Ananda Integrative Healing Group, has several therapists and surrogate partners who mostly see clients who have experienced trauma or sexual abuse or who have certain kinds of disabilities.

“If any kind of sexual contact is included in the work, it’s done after months of other types of work with a licensed therapist overseeing it,” she said. “So anybody who just wants to have some kind of sexual experience, they can do it a lot faster and a lot cheaper by just finding a regular sex worker, which I personally think also should be legal and protected.”

According to Ms. Ananda’s research and conversations she has had with other surrogate partners, only about 5 to 10 percent of cases of surrogate partner therapy involve sex acts.

This work takes time. For example, if body-image issues are a problem, about three or four months into the therapy, a surrogate partner may invite the client to do a mirror exercise: Look at yourself naked in a full-length mirror, the surrogate will instruct, and be honest about what you feel about your body and its different parts.

“The potential for actual sexual contact makes it real, so to speak,” Mr. Heartman said. “It actually makes the environment so much more realistic that every part of the process becomes much more effective because the client realizes that this is leading somewhere.”

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