Real Housewives of Beverly Hills star Kim Richards checked in a rehab facility this week, joining a slew of other Hollywood stars who have dealt with their demons in a treatment center.

RadarOnline.com has photos of all the biggest names in the business, from chart-topping singers to Academy Award winning actors, who have admitted to undergoing rehab programs to deal with their problems.

PHOTOS: Hollywood Stars Who Have Been To Rehab

What do Charlie Sheen, Robert Downey Jr. and Demi Moore have in common? All three Brat Packers have attended treatment programs. While Demi only went to rehab once in the 1980's to deal with a cocaine problem, Sheen and Downey have done the nationwide tour, attended several different programs over the years.

Entourage star Jeremy Piven is dating Jason Wahler’s former fiancée Katja Decker Sadowski, RadarOnline.com can exclusively reveal.

Ladies-man Piven, 45, who has been linked to model Ashley Chontos, January Jones and Dita Von Teese in the past, was spotted walking hand in hand with the 22-year-old blonde beauty Katja at the Arc Light Cinema in Los Angeles on Sunday.

Law student Sadowski and Wahler called off their engagement in February, 2009, triggering a series of legal troubles for the reality television star, culminating with his decision to enter rehab.

VIDEO: Jeremy Piven Screams & Swears At Tonight Show Intern In Fishy Prank

One source told RadarOnline.com: “Jeremy and Katja looked really happy at the cinema – they were holding hands as they waited in line to see the movie King’s Speech on Sunday night and they were kissing and cuddling one another throughout the film too.

Reality television bad boy Jason Wahler has falled off the wagon after a stint in Celebrity Rehab, RadarOnline.com has exclusively learned.

"Things were going so well for Jason until last week," said a source, close to the former Laguna Beach star.

PHOTOS: Cast Of Celebrity Rehab 4

Last week, Wahler was photographed at Hollywood hot spots Boa and Katsuya.

Janice Dickinson and Rachel Uchitel were roommates on Celebrity Rehab 4 but the arrangement didn't last very long and the feuding duo had to be separated by staff, RadarOnline.com learned exclusively.

PHOTOS: Cast Of Celebrity Rehab 4

According to a show insider, the two "were practically at each other's throats from the beginning. They fought constantly, and Dr. Drew and the staff ultimately made the decision to separate the two as they were just being so disruptive to everyone involved. It was just way too much ego in one room.”

PHOTOS: Celebs With Drinking Problems

As RadarOnline.com previously reported, Rachel bolted from the show for 24 hours, holed up at a swanky Beverly Hills hotel, but and was lured back by producers the next day. "Rachel just couldn't stand even being in the same vicinity as Janice, and the tension that Rachel was dealing with because of it was one of the reasons that she left,” the insider added.

PHOTOS: Janice Dickinson And Jeremy London Check Into Celebrity Rehab

“Janice was hoping she wouldn't come back, but Janice predicted that Uchitel would ultimately comeback because she missed the cameras. It drove Janice over the edge that Rachel thought she was a celebrity. Both of these women are dealing with major self esteem issues, along with their personal addictions.”

PHOTOS: Rachel Uchitel In St.Barth With Ryan Seacrest

The cast graduated earlier this week with Jason Davis, Jeremy London, and Jason Wahler continuing inpatient treatment at another facility, RadarOnline.com has confirmed. BET reality TV star Frankie returned to Atlanta and is preparing to enter an after care center there. Neither Rachel nor Janice are continuing treatment in a facility, but both are following a care plan that was given to both of them.

Celebrity Rehab 4 is scheduled to premiere in October on VH1.

Only on reality TV.

PHOTOS: Cast Of Celebrity Rehab 4

A hodgepodge of famous faces were seen on the set of VH1's Celebrity Rehab with Dr. Drew in Pasadena Saturday, and RadarOnline.com has the  just-released pics for you.

Eric Roberts, the older brother of Oscar-winning actress Julia Roberts, has joined the cast of VH1’s Celebrity Rehab 4, RadarOnline.com has learned exclusively.

The 54-year-old star of such films as The Dark Knight and Fight Club, has moved into the Pasadena Recovery Center and is bunking with former Mallrats star Jeremy London.

“Eric Roberts is my roommate and is simply amazing,” London told RadarOnline.com. “He’s an incredible person.”

Rachel Uchitel is the newest addition to Celebrity Rehab, and RadarOnline.com has learned Ambien is the drug of choice that landed her there.

We've also learned that she did the drug with Tiger Woods, using it to enhance sex.

In email messages between Uchitel and Woods, obtained exclusively by RadarOnline.com, Tiger asks for Ambien and Rachel says she's worried about being addicted.