Heterosexual women have fewer orgasms than men or lesbian or bisexual women, a study suggests.
The findings came from a study of 52,600 people in the US, exploring the "orgasm gap" between the genders and different sexual orientations.
The report in Archives of Sexual Behaviour revealed a "variety of behaviours couples can try to increase orgasm frequency".
These include oral sex and manual stimulation.
The study, by Indiana University, Chapman University and Claremont Graduate University, showed the proportion of people who usually orgasmed was:
- 65% of heterosexual women
- 66% of bisexual women
- 86% of lesbian women
- 88% of bisexual men
- 89% of gay men
- 95% of heterosexual men
The research team said: "The findings, however, indicate that this orgasm gap can be reduced.
"The fact that lesbian women orgasmed more often than heterosexual women indicates that many heterosexual women could experience higher rates of orgasm."
Few heterosexual women climaxed through penetrative sex alone, the report said.
The study showed that "of particular importance was incorporating oral sex along with other activities during a sexual encounter".
There was a clear pattern between more oral sex and more orgasms in heterosexual women, lesbian women, bisexual women, gay men and bisexual men.
Only in straight men was no link detected.
Other behaviours linked to greater orgasms in women were:
- Asking for what they wanted in bed
- Praising their partner for something they did in bed
- Calling or emailing to tease about doing something sexual
- Wearing sexy lingerie
- Trying new sexual positions
- Anal stimulation
- Talking about or acting out sexual fantasies
- Engaging in sexy talk and expressions of love during sex
The report authors said there were both social and evolutionary ideas around why men and women have different rates of orgasm.
For example a stigma against women expressing sexual desire hampering sexual discovery and a belief in some men that most women orgasm from penetrative sex.
And from an evolutionary perspective they suggested the male and female orgasms served different purposes which could also have an effect.
This male orgasm is all about ejaculation to ensure reproduction while in women it "facilitates bonding with a long-term romantic partner", the report said.