Locking lips can have some unexpected consequences, with a new Melbourne study finding gonorrhoea is being transmitted through kissing.

Researchers surveyed more than 2000 men at the Melbourne Sexual Health Centre and found that throat gonorrhoea was being passed on without any contact to a sexual partner's genitals.

"This actually changes what we have believed over the past 100 years," Associate Professor Eric Chow told AAP.

"Traditionally we thought gonorrhoea was mainly transmitted through penetrative sex, but the recent data actually showed there's quite a lot of infection in the throat.

"So we tried a different line of possible transmission routes ... and we found kissing was a significant risk factor for gonorrhoea in the throat."

He said there were often no symptoms for people with throat gonorrhoea, so it was easy to pass on the infection without realising it.

When the infection is detected in the genitals, there are more obvious symptoms such as swelling, itchiness or bleeding.

Men who are gay or bisexual or those who have sex with other men are the most at-risk group for gonorrhoea.

But Prof Chow said there was an increasing number of cases of the sexually transmitted disease in heterosexual men and women.

"We are actually seeing rises across the country," he said.

"This is a concern because we know there's antibiotic resistance for gonorrhoea, so that actually makes the infection more difficult to treat.

"We need to have a better understanding of how the infection is transmitted in order to think about what we should do and what interventions would help to control the infection."

Prof Chow said this latest research could help with those questions and ensure the public is better informed about sexually transmitted infections.

"If you have sexual contact or if you are sexually active you should get a regular STI screening because some of the cases will be asymptomatic," he said.