From Ben and Jen, to Vince and Jen, to Brad and Angelina, the on-set romance is a time-honored Hollywood tradition. And SHOWBIZ TONIGHT is here to tell you, that tradition is alive and well.

Brad Pitt and Angelina Jolie are the poster couple for falling in love on set.

Come on, honey. Come to daddy. [Brad Pitt in "Mr. and Mrs. Smith"]

You could almost see the sparks fly when Brad and Angelina co-starred as husband and wife in "Mr. & Mrs. Smith."

When there are sex scenes in the films, you could almost expect that something is going to happen. People want to see the chemistry on the screen.

And people did. That movie set the rumor mill spinning, especially since Brad was still married to Jennifer Aniston when he shot those steamy scenes with Angie.

But Brad Pitt falling for Angelina Jolie was not just about being on set and being lovers. She was also his ticket to doing something important in the world. The fact that she's a UN ambassador and traveling all over the place, he wanted to do that. So there was a bigger package for him.

Angelina's not the only actress who mixes business with pleasure. Jennifer Garner met her first husband, Scott Foley, on the set of "Felicity". Then came boyfriend and "Alias" co-star Michael Vartan. And then came Ben Affleck, who she met when they co-starred in "Daredevil".

Nice to meet you. [Jennifer Garner in "Daredevil"]

Now Ben and Jen are married, with a kid.

There are so many elements that add to the possibility of falling in love on the set. Indeed, you're isolated. You're spending an enormous amount of time with one another and you're separated from your own home life.

Before that Ben and Jen, there was this Ben and Jen. Jennifer Lopez and Ben fell for each other on the set of "Gigli". That movie flopped, and eventually so did the romance.

You're not my type. Good night. [Jennifer Lopez in "Gigli"]

The bubble that's created on set when you're in that romance can certainly burst and be over when you go back to your own life, and when you're distracted or when you're on the next movie set.

Maybe that's what happened to Julia Roberts, who hooked up with a long list of leading men, including Liam Neeson, Dylan McDermott, Kiefer Sutherland, Lyle Lovett and Matthew Perry.

She's now married to cameraman Danny Moder. And get this: she met him, where else? on the set of "The Mexican".

With all this canoodling between co-stars, SHOWBIZ TONIGHT can tell you, there is a way to keep famous relationships safe.

One way is to have a life that is away from Hollywood. So you have someone like Julia Roberts, who's now living in another state, happily married to Danny Moder, raising her kids. Goldie Hawn has that, too. She has a house in Utah.

Speaking of Goldie Hawn, guess where she met Kurt Russell, who's she been with for 24 years? On the set of their 1982 movie "Swing Shift". Goldie's daughter Kate Hudson may have learned a thing or two from mom. Kate, who has split from Chris Robinson, has been quietly stepping out with her "You, Me and Dupree" co-star Owen Wilson, although the two have never confirmed the relationship.

In the long run, if somebody is going to fall for their co-star, and leave you for somebody else, you need to just say, "You know what? There was nothing that I could to stop that from happening."

And as SHOWBIZ TONIGHT has shown you, it is something that happens plenty in Hollywood.