Scientists say they have discovered a formula for creating sexual chemistry on the movie screen.
The experts gave Titanic zero out of ten for sexual chemistry
The experts, from King's College in London, watched romantic films to come up with the right formula.
They said voice, eye contact, body language and excitement could be used to measure sexual chemistry.
When Harry Met Sally, starring Meg Ryan and Billy Crystal, scored a top rating of 10 out of 10 for sexual chemistry, while Casablanca was second.
10/10 - When Harry Met Sally (Meg Ryan/Billy Crystal)
9.5/10 - Casablanca (Ingrid Bergman/Humphrey Bogart)
9/10 - Breakfast at Tiffany's (Audrey Hepburn/George Peppard)
9/10 - Lost in Translation (Scarlett Johansson/Bill Murray)
7/10 - Pretty Woman (Julia Roberts/Richard Gere)
The newest film in the study, Lost in Translation, scored nine out of ten for "the subtle relationship" portrayed by Scarlett Johansson and Bill Murray.
Breakfast at Tiffany's and Pretty Woman also scored well, but Hugh Grant and Sandra Bullock failed to light up the screen in Two Weeks Notice, which received just two out of 10.
The scientists also found that Titanic, starring Kate Winslet and Leonardo DiCaprio, contained no sexual chemistry, despite winning a clutch of Oscars.
A King's College psychiatrist said: "In Titanic, the way they speak to each other isn't natural. It just doesn't come across as genuine.
"In Ghost, Patrick Swayze's desperate and sad lines as he tries to communicate to his wife shows perfect use of voice."
Falling in love
The researchers also looked at how actors use their eyes to convey sexual
"When Meg Ryan's character Sally shows that it's easy to fake an orgasm by giving a demonstration in a restaurant, you can see Billy Crystal's
character Harry look at her in a different way."
"For the first time, he looks at her with different eyes and the floodgates open."
The experts used the scene in Dirty Dancing where Patrick Swayze and Jennifer Grey take over the dance floor as the perfect example of body language.
Experts said the sense of excitement and anticipation conveyed while falling in love was also important.
Experts claim "when Harry finally confesses to Sally he is in love with her no one can help but feel a slight butterfly in their tummy".
"In Titanic, there isn't any of that, they confess their love for each other pretty quickly."
The research was carried out for Sky Movies.