Zac Efron

Pals of actor Zac Efron allegedly fret the Hairspray heartthrob is going off the rails, with an insider sharing there's 'growing concern' about his alleged 'erratic behavior.'

RadarOnline.com rounded up some of the celebrities who ended up in rehab due to their substance abuse.

Sources say the former teen heartthrob was hurt by the lack of support for his show.

She is spilling more about their time together.

The actor is unbothered by the allegations.

She didn't hold back about her experience dating the 'High School Musical' star.

The High School Musical star has yet to respond.

"I can confirm I know this person and it is true," says an Australian influencer.

The 33-year-old actor celebrated Earth Day with the debut of a new face.

13 chilling true crime films to stream (if you dare!)

The stars called it quits after nearly nine years together.

All of these celebs’ abs are chiseled to such perfection, enjoy the view!

New situation 'could push him' over the edge.

Click through ten photos of the shirtless bros’ bicep-bulging war.

'Proud of all the hard work he put in,' boasts co-star Dwayne 'The Rock' Johnson

See the photos of Zac's hot body!

Friends concerned over Gomez & Efron's new fling.

Take a look at Zac Efron's sexiest shots!

How Hollywood melted down when naked pics of the star hit the net.

Which stars have taken the time to Tinder-ize?

By Leah Ornstein - Radar Features Editor Still need a little Halloween inspiration? Hollywood stars love getting dressed up for the spookiest day of the year,

The two stars reportedly hooked-up via a dating App.

The actor's clean-cut 'High School Musical' days are clearly over.

‘Just for fun.’

By Radar Staff Zac Efron and Ashley Tisdale showed off two of the best bods in Hollywood Saturday, as they took to the beach in Malibu for an afternoon of fun

By Leah Ornstein - Radar Style & Beauty Editor These smokin’ hot stars manage to steam up the beach on their own, but when they bring along their equally sexy

By Leah Ornstein - Radar Style & Beauty Editor Bikini babes aren’t the only ones stripping down and having fun in the sun. From teen heartthrobs to burley

Demi Lovato, Bethenny Frankel, Laverne Cox & more!

See which guys are the most-searched stripped-down celebrities of the year.

"Right now I'm probably the physically strongest I've ever felt," he said.

See your favorite stars in need of a serious dab of deodorant.

Loser gets drawn on!

See the steamy new 'Baywatch' cast photos!

Watch the hilarious skit.

Zac Efron was caught in a compromising situation Tuesday, as he was photographed nearly naked with his hands down his pants! It was all part of the fun on the set of his new film, Neighbors 2. Click through the gallery to see all the fun photos!

Find out why Zac Efron's friends are worried sick about him and fear he may have relapsed after he went MIA amid trouble with girlfriend.

The massive flop of the drug-and-party-themed We Are Your Friends has folks on the set of his new flick Neighbors 2 petrified that rehabbing Zac Efron has jumped feet-first off the wagon.

Not every star burns bright at birth! Some of the biggest names in showbiz had to outgrow some awkward high school years…

Find out why David Hasselhoff is hesitant to sign on to the 'Baywatch' movie, as a source tells Radar whether jealousy of Zac Efron or greed is preventing his decision.

Money is no object for celebrities when it comes to purchasing their dream homes! From Jennifer Lawrence’s $8.2 million mansion to Taylor Swift’s $19.9 million penthouse, go inside the most luxurious homes of Hollywood’s rich and famous!

With summer in full swing, RadarOnline.com has the best celebrity beach bods lined up just for you! See the photos.

It's been seven years since High School Musical star Zac Efron last reprised the role that made him a movie star. Since then, the 27-year-old heartthrob has done nearly a dozen movies while at the same time battling serious demons. Now, RadarOnline.com has exclusively learned that Efron has finally managed to clean up his act, and is ready for a huge career comeback in the much-anticipated High School Musical 4.

Click through RadarOnline.com's gallery to see Zac Efron in all his tight spandex glory on the Hawaii set of his new movie Mike and Dave Need Wedding Dates.

Could he be any sexier? Zac Efron sports a rock-hard bod in Hawaii with Mike and Dave Need Wedding Dates co-stars Adam DeVine and Aubrey Plaza.

The naked escapades continue for Zac Efron on the set of his new blockbuster Dirty Grandpa, also starring Hollywood alum Robert De Niro. But this time, Efron flaunted a new view – the rear view – along with his butt double.

Zac Efron, this is your future — if you're lucky! The 27-year-old compared notes and muscles with acting legend Robert De Niro, 71, on the set of Dirty Grandpa in Georgia today, and RadarOnline.com has the jaw-dropping photos.

Zac Efron stripped down to his underwear while filming a scene for his newest movie, Dirty Grandpa, today on Tybee Island, Georgia. Click through these 9 super-sizzling photos of the nearly naked hot-bodied star bearing almost all!

Click through these 10 photos of Zac Efron’s journey from teenage movie star, to rehab to his sober life now and find out why is friends say he is ready for a career comeback.

The 15 most sought-after male stars and photos from their steamiest nude scenes. Check out Brad Pitt, Mark Wahlberg, Zac Efron and more!

Here are 57 of Hollywood’s most hated celebs!