Meiwes said there were "hundreds, thousands" of people seeking to fulfil their desires to eat humans or be eaten via Internet advertisements in forums called "Cannibal Cafe," "Guy Cannibals" and "Torturenet."
In testimony so frank it drew gasps from the public gallery, Meiwes said he had kept his victim's skull and plastic bags of flesh in his freezer. He ate about 44 pounds of the flesh, defrosting it bit by bit.
"With every piece of flesh I ate I remembered him," Meiwes, a self-assured and well-spoken computer repair man, told the judge. "It was like taking communion."
The killing took place in March 2001. Meiwes was arrested in December 2002 after police received a tip-off from someone who had seen one of his Internet adverts seeking a slaughter victim.
The trial is expected to last until the end of January and some 40 witnesses will be called, including some of Meiwes's Internet contacts.
The gaunt, bespectacled defendant said that during his upbringing alone with a dominant mother he had longed for a little brother he could make "part of me."
He told how he made contact online with a 43-year-old Berlin computer specialist identified only as Bernd-Juergen B.
He invited him to his elegant half-timbered home near Kassel and killed him with a kitchen knife in a "slaughtering room" he had built containing meat hooks, a cage and a butcher's table.
"He told me he had had the desire since he was a child to be slaughtered and eaten," Meiwes said. "He was very intelligent and I didn't see any sign that he was disturbed." Meiwes filmed the killing and the video tape may be shown to the court.
Defense lawyers have said the film shows Meiwes cutting off the victim's penis at the latter's request.
"It was important to him that his member be cut off and that he witness it," Meiwes said.
"He screamed terribly and jumped around the table but after a while he said he was surprised it didn't hurt and was very pleased that the wound bled so strongly," he added.
"It gave him pleasure."