Zac Efron is set to challenge Adrian Grenier for the title of top TV hunk - the teen heart-throb is to join the cast of Entourage.

The High School Musical star filmed a cameo appearance for the hit HBO show at a Beverly Hills shoe store on Tuesday.

A source tells E! Online, "He was filming a scene and talking on his cell phone. None of the other Entourage cast was here. He was really nice."

The sixth season of Entourage will see Grenier line up against a string of celebrity guests including rapper Lil Wayne and supermodel Gisele Bundchen's sports star husband Tom Brady.

The season begins in on July 12.

Zac Efron Gallery

(This news article provided by World Entertainment News Network)