The Mini, which is held May 3, is sold out with 35,000 entrants.
Event organizers also are challenging those registered for the Mini to do both events and join the "May Marathon Club."
Race Around the Reservoir is set for May 17, and will follow a course near Geist Reservoir in Marion and Hamilton counties. Like the Mini, the event will consist of 13.1-mile and 3.1-mile races.
Race Around the Reservoir organizers expect as many as 3,000 participants for their inaugural event.
"It's really difficult to say how many people we'll get," said Vince Auten, marketing director for The Geist Half Marathon Inc., a not-for-profit organization conducting the race. "With the Mini selling out, people are obviously wanting to do an event like this."
The Geist race was started to establish an annual race with a growing following in the Marion-Hamilton county area, Auten said.
Half-marathon registration costs $40 - $10 less than the Mini Marathon. The fee for the shorter race is $20.
Participants who complete the 500 Festival Mini and Race Around the Reservoir half-marathon will be guests at a special reception and get a special commemorative T-shirt, Auten said.
All proceeds of the race will go toward fitness programs held in conjunction with Marion and Hamilton county schools.
Event organizers said that despite the Mini's date, May is the best time for their event.
"We wanted to do it before school was out due to our charitable cause," Auten said. "Summer is too hot, and we didn't want to conflict with the travel season."
Organizers considered a fall date, but the date conflicted with several 26.2-mile marathons in the region.
Event director Jeff Graves is marketing Race Around the Reservoir by promoting its scenic course, which includes winding, tree-lined roads, five lake crossings with panoramic views and a picturesque finish near the water's edge at Geist Marina.
Don Carr, the Indianapolis 500 Festival Mini-Marathon course director, has been hired to oversee Race Around the Reservoir course logistics.
The board of directors for the new event includes Runner's Forum owner Marty Day; Tom Britt, publisher of atGeist.com; and Graves, president of locally based Vision Event Management and former Indianapolis 500 Festival Mini Marathon executive director.
More information is at www.geisthalf.com.