We search for chemistry in our personal relationships and it’s what makes for a successful onscreen romance. When the leading lady and the leading man look at each other and the audience can feel the smoldering heat, that's chemistry.  In survey jointly conducted by ABC News and People magazine a "Best in Film" list was formed announcing the top five most romantic movie couples:

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5. Spencer Tracy and Katharine Hepburn: 10%
Tracy and Hepburn were so dynamic on screen that they starred together in nine films, beginning with "Woman of the Year" in 1942, as well as "Without Love" and "Adam's Rib." Some insist the latter was their best film. They were known for their "perfect blend of sweetness and sexiness, humor and passion," reports ABC News. Although they never married, Spence and Kate had a lifelong off-screen romance.

4. Humphrey Bogart and Ingrid Bergman in "Casablanca": 12%
Morocco. World War II. A smoky nightclub. A piano. Mix together with the star power of Bogart and Bergman playing former lovers, Rick Blaine and Ilsa Lund, and you have the 1942 classic "Casablanca."

3. Richard Gere and Julia Roberts in "Pretty Woman": 14%
This is the modern-day Cinderella story about the impossibly rich, hardnosed businessman Edward Lewis and the scrappy and beautiful hooker Vivian Ward, played so expertly in the 1990 film, "Pretty Woman," by Gere and Roberts that they went on to star together in "The Runaway Bride."

2. Clark Gable and Vivien Leigh in "Gone With the Wind": 15%
With her flashing eyes and beautiful face and his roguish good looks, Leigh and Gable will live forever as Scarlett O'Hara and Clark Gable in the 1939 film "Gone With the Wind," based on the bestselling book by Margaret Mitchell. How can anyone forget that kiss--passionate and fiery as Atlanta burns behind them? He loves her. He hates her. And he can't live without her.

1. Leonardo DiCaprio and Kate Winslet in "Titanic": 23%
As star-crossed lovers Jack and Rose, DiCaprio and Winslet not only broke box office records in the 1997 movie "Titanic," but also a lot of hearts in the memorable and steamy (literally!) love scenes. "Leo loves Kate Winslet so much in 'Titanic' he willingly falls to his death at the end in the icy waters, giving her the raft," Los Angeles Times awards expert Tom O'Neil told ABC News. "These two don't just love each other. They really, really love each other through the ages...They're ghosts at the end, and they still love each other even though the ship's gone down."