May is an especially good month for competitive sport in Baltimore. There is of course the hoopla over the Preakness. Johns Hopkins played in the Division I lacrosse championship game. The Orioles still have a palpable pulse. High school championships abound.

And though not as well known, Monsterball season is under way.

What, you may ask, is Monsterball? It's a cross between baseball and kickball, invented by Friends School senior Bradley Kolodner of Guilford, and played by 15-20 kids and adults several times a month on a field with base lines, a fenced back stop, a tulip tree and a trampoline in Bradley's backyard on Fenchurch Road.

Basic equipment is a standard aluminum baseball bat, four bases and a play ball -- those large, brightly colored, plastic balls you can buy at the supermarket.

Here's how you play: A pitcher throws the ball and a batter swings at it. If the batter makes contact, which is often, given the size of the ball, he or she then runs the bases. Fielders can record outs by catching the ball in the air, hitting the runner with the ball, or throwing the ball to a baseman. There are normally four or five fielders at a time.

In addition to the backstop and the base lines, the field includes trees painted yellow to mark foul lines; yardage signs including 81 feet to center and 64 feet down the left-field line; a scoreboard, and 2,400 watts of night lights mounted on the back, side and backstop fences.

There's an uptick in energy use during games, says Bradley's mom, Alison Brown, an administrator for the University of Maryland Medical System.

Home runs are scored by hitting balls over the fence. However, that means hitting the ball into someone else's yard. Fortunately, the house beyond center field is vacant. It's also the longest way out -- and you must clear several large trees.

The right-field fence is protected by the trampoline (home run if you land the ball in it) and the tulip tree.

The biggest problem is if you hit a foul ball over the left- field fence/garage boundary. These balls cannot be retrieved because the owner of that property doesn't return them or allow players to retrieve them. To discourage players from hitting the ball there, it's an automatic out.

Other than that, it's an easy game to play. Really, who couldn't hit a ball the size of Uncle Fester's head? Also, it is nearly impossible to get hurt by a play ball, no matter how hard you hit it or throw it at someone.

Bradley adapted the game about six years ago from a game his uncle, Tim Short, taught him during a family vacation in Middlebury, Vt.

"It just stuck with me," Bradley said. "I sort of took it a few steps further. Each year I make one or two additional field improvements."

Bradley, as a sign on the backstop declares, is the commissioner of Monsterball. All disputes during games are settled by him. The consensus among players is that as the creator of the game, provider of balls and designer of the field, he should make the close calls.

The score was a little lopsided on Sunday, May 4, 19-4, and the big hitter of the evening was James Sakomoto-Wengel, a Friends senior, who went 6-for-7 with five home runs.

But nobody cares that much about winning or losing. The players, 12 to 18 (including Bradley's sister, Hillary, 15), seem more interested in having a good time, heckling one another and speculating on why some of their friends aren't there -- the most popular guess being that they've been grounded.

Players also speculate about when "freezie pops" will be distributed. Each side hopes this will occur while they are batting, so they get first crack at the best flavors.

But Bradley is serious about his sport. He wrote a three-page rule book. When he applied to colleges and universities, his essays were about Monsterball, why he created it and how it became a social networking event as much as a game.

He plans to major in journalism at Ithaca College in New York, and start a Monsterball club there.

But he fears for the future of his game and his field in Guilford.

"My parents and my sister really want a pool in the backyard," he said. "There goes years of building this cool field."

His dad, Kenneth Kolodner, doubts that a pool is in the family's foreseeable future.

"All the kids around here are asking, 'What's going to happen when Bradley goes to college?' " said Kolodner, a professional musician who plays the fiddle and hammered dulcimer, gives private music lessons and is a member of the world folk band Helicon.

Kolodner sees it as a good thing for the neighborhood that youths from all over are coming to the family's backyard to socialize.

"You just don't see that so much today," he said.

Editor Larry Perl contributed to this story.

Louisa Peartree is the Keswick neighborhood columnist for the Messenger.