Ernst Zündel, who from a ramshackle Victorian house in central Toronto churned out books, posters, audiotapes and memorabilia denying the Holocaust and spreading neo-Nazi messages worldwide, died on Saturday at his home in Bad Wildbad, Germany. He was 78.

The death was confirmed by Marina Lahmann, an official in the town. No cause was provided.

Mr. Zündel was convicted twice, in 1985 and 1988, under a rarely invoked law criminalizing the knowing publication of false news that caused, or was likely to cause, harm to the public interest, which the authorities interpreted to include Canada’s commitment to tolerance.

But both convictions were overturned, and critics said the prosecutions, however well intentioned, did more harm than good by giving Mr. Zündel and other Holocaust deniers, including Robert Faurisson of France and Ditlieb Felderer of Sweden, a platform and a chance to bring truth itself into disrepute.

Mr. Zündel showed up at court wearing a hard hat and a bulletproof vest, claiming to be the victim of a conspiracy to silence him. Renowned historians, including Raul Hilberg and Christopher Browning, were subjected to withering cross-examination. Several Auschwitz survivors, among them Dennis Urstein and Rudolf Vrba, gave grueling testimonials about what they had endured.