While Baltimore sleeps, Michael Phelps will begin his quest to make Olympic history.

The first swimming final at the Athens Olympics for both men and women is the 400-meter individual medley, a one-day, two-round test where Phelps and Katie Hoff, another product of the North Baltimore Aquatic Club, are expected to win medals of assorted luster.The first of a program that could add up to 18 races for Phelps comes in tomorrow morning's preliminaries, when he figures to race at approximately 10 a.m. Athens time, 3 a.m. in Baltimore.

Hoff makes her Olympic debut some 40 minutes later. The top eight finishers return for tomorrow evening's finals.

Phelps has four of history's five fastest times in this event. He lowered his world record to 4 minutes, 8.41 seconds last month at the U.S. trials. Laszlo Cseh, an 18-year-old Hungarian, went 4:10.79 in taking silver at last year's world championships, but he suffered a broken foot on the pool deck in July.

Cseh told a Hungarian journalist he has been training regularly, but still feels pain in the foot. Cseh, Italian Alessio Boggiatto and Erik Vendt, a U.S. teammate of Phelps', are expected to contend for the silver medal.

Phelps anticipates no problems in the preliminaries, which provided some chills and thrills for Hoff at the trials.

When Hoff won at the Spring Nationals and at the U.S. trials, she cut huge chunks of time from the morning to evening. A dawdling preliminary swim here would keep her out of the eight-person final.

"It's not like I mean to do it; I just messed up," Hoff said. "I've been conscious in practice of feeling the stroke [butterfly] in the first 50 [of the opening leg]. In trials, my tempo was so fast, but I've been working on that."

Hoff's trials time, 4:37.67, is the fastest in the world this year. Yana Klochkova of the Ukraine set the world record of 4:33.59 when she took gold at the 2000 Olympics. Hungary's Eva Risztov is another factor.