When Monteith and Rand leave the Kreeger Theater's stage for intermission -- after such zany routines as getting stoned with a fly, and weird improvisations that find them fishing on the moon -- you wonder if they really plan to return for another hour. When they do, with a mention that they'll be at the Kreeger for a four-week run, you decide that they must be crazy.

Judging by their comedy act -- in which John Monteith and Suzanne Rand unleash enough raw energy to power a couple of large cities -- they probably are. There seems no other explanation for people who spend so much of their soul and wit on a single night, and then come back for more.

But first things first: Monteith and Rand are funny. They are usually very funny, even as they take risks in the Arena that haven'tbeen seen since the days of Roman gladiators. This is a daredevil business, with death always in the balance, and it's exhilarating when they escape without a scratch.

Monteith of Philadelphia and Rand of Chicago -- both steeped in the tradition of improvisational comedy -- joined forces six years ago and took their act on the road. They have since stirred it to a maniacally pitched whirlwind that sweeps up everything in its path. "Just pretend that you're in your own theater at home," says Rand, coaxing the crowd to help them improvise a sketch.

The crowd helps, of course -- which accounts for much of the fun. It gives the happy illusion that you, too, can get laughs.

With audience-supplied phrases, the team makes up witty songs. In one improvisation the other night -- a detective spoof -- the audience managed the sound effects. For another, following shouted commands, the duo prepared a White House dinner with such imaginary implements as Popeil Pocket Fisherman and ginzu knie -- in such theatrical styles as Kabuki, Stephen Sondheim, Alfred Hitchock, Ingmar Bergman, Eugene O'Neill, Moliere and Shakespeare.

Their set routines, with such topics as critics at a porno flick and a stewardess landing a jetliner, are amusing but not antic. Monteith and Rand, lightning-quick and goose-loose, do their best work when required to wing it. They have, in spades, the gift of comics and gladiators both: grace under pressure. MONTEITH AND RAND -- At Arena's Kreeger Theater through January 2.