University of Arizona students are set to run around campus in their unmentionables tonight — and this time it's "official."

While there have been similar run on campus since at least 2009, tonight's event is being put on by ZonaZoo.

Students will strip to their undies and the clothes will be donated to the Tucson Unified School District's clothing bank, according to a Facebook page promoting the run.

The notice for tonight's "Running of the Cats" includes a warning to avoid anything too sheer and this, "You do not have to run in your underwear, but you cannot run naked."

It starts at 6 p.m. near Old Main.