Britain's Chris Boardman took third place, the bronze providing him with his fourth medal in this event in six years.

Sweden's Michael Andersson was a surprise silver medallist.

Boardman: Fourth medal in six years of world time trials

Ullrich's first senior world title confirms a spectacular comeback after criticism over his winter weight problems before injury ruled him out of the Tour de France.

Last month he returned to form to win the three-week Tour of Spain - the "Vuelta" - confirming his status as favourite for this event.

"Although I missed the Tour these are great victories, and I can say my season was successful," he said after this victory.

"It's always great to win, but to finally be a world champion is a beautiful thing. It'll be hard to criticize me now."

Boardman plans to retire after next season and was satisfied with his performance here.

"When I saw Ullrich at the Vuelta, it was clear he would be difficult, verging on impossible, to beat, considering his form," admitted the Briton.

Andersson's result was a surprise considering that he has not raced for a month-and-a-half because of the disbandment of his Danish team.

"I went home to Sweden, and trained in temperatures of eight degrees celsius and in rain each day. So it is a big surprise," he said.

Dominant German

Ullrich covered the 50.6km course in and around Treviso, northern Italy, in 1 hour, 28.44 seconds.

Andersson was the only rider close to him, 14 seconds behind, while 1994 winner Boardman of Britain was 59 seconds adrift.

The result was a reverse of the 1994 race in Sicily, where the young Ullrich made his breakthrough with bronze behind the Briton.

This year the German went through every intermediate check in the quickest time.

Andersson, an earlier starter, was never out of the top three, although Boardman's times fluctuated widely over the second half of the circuit.

Ullrich: Powerful ride follows Tour of Spain win

After 21km the Briton was in second, 24 seconds adrift of Ullrich and a second clear of Andersson.

But the next six kilometres saw the Briton drop 51 seconds back as former medallists Mechior Mauri and Alex Zulle moved up the leaderboard.

But Boardman gave it his all and after 50 minutes of racing he was back up to third.

The Briton was the fifth-last man to finish, with Ullrich the penultimate rider, arriving to great celebrations from German spectators.

Only Ukrainian Sehi Honchar could now take Boardman's medal from him.

But the 1998 bronze medallist, going out last in the absence of injured defending champion Abraham Olano, could not repeat his performance of last year.

Moldovan thrown out

Before the race, Moldova's Igor Bonciucov became the first rider banned at these championships because of an elevated red blood cell count.

Thirty-seven riders have passed these checks this week.

After Thursday's travel day, the championships resume on Friday in Verona with the road races, culminating in Sunday's men's elite event.

Ullrich warned the other favourites for that race that he is keen for an unprecedented double.

"I'm confident, I'm in good shape, and I have a good team," he said. "We'll see what happens Sunday."

Result:

1. Jan Ullrich, Germany, one hour, 28.44 seconds, or 50.209 kph (31.129 mph)
2. Michael Andersson, Sweden, 1:00:42.53
3. Chris Boardman, Britain, 1:01:27.10
4. Raivis Belohvosciks, Latvia, 1:01.32.94
5. Melchior Mauri, Spain, 1:01:47.25
6. Sergei Gontchar, Ukraine, 1:01:47.97
7. Gilles Maignan, France, 1:01:53.84
8. Erik Dekker, Netherlands, 1:02:09.03
9. Jens Voigt, Germany, 1:02:13.55
10. Alex Zulle, Switzerland, 1:02:14.23
11. Vjatceslav Ekimov, Russia, 1:02:22.03
12. Eugen Wacker, Kyrgyzstan, 1:02:28.96
13, Andrei Teteriouk, Kazakhstan, 1:02:29.78
14. Alvaro Gonzalez de Galdeano, Spain, 1:02:41.75
15. Marco Velo, Italy, 1:02:42.83
16. Raimondas Rumsas, Lithuania, 1:02:44.16
17. Cristophe Moreau, France, 1:02:47.84
18. Arturas Kasputis, Lithuania, 1:02:48.53
19. Beat Zberg, Switzerland, 1:02:50.45
20. William Chann McRae, United States, 1:02:55.37