If you notice a bunch of people running through downtown Cheyenne in their underwear tomorrow, don't be alarmed, the scantily clad athletes will be part of "Cupid's Undie Run".

Billed as the "largest pantsless party" in the country, the "brief" one-mile run is a fundraiser for neurofibromatosis, a genetic disorder that affects 1 in every 3,000 children born, and the Children's Tumor Foundation. Since the inaugural Undie Run in Washington D.C. in 2010, the charity has expanded to 40 cities around the world.

"We encourage undies, but we get that it’s not for everyone," said Cheyenne Race Director Melanie Manchester. "Whether you start a team with your friends, join a team, or run solo, just come out, have a blast, and raise some money for NF research!"

The event kicks off at noon, with check-in and registration on the second floor of the Asher Building on 500 W. 15th St. The run begins at 2 p.m. with an after-party to follow. Registration is $45 in advance, $50 at the door. The temperature is expected to be around 32 degrees at race time.