He said on Wednesday that the authorities had given him no indication of why he had received his passport now. “I only can say why not? They have promised for the past four years to give it back. Now finally they gave it to me,” he said in a telephone interview. “They always say it’s in the process but I just need to be patient.”

The confiscation of his passport meant that Mr. Ai was forced to organize his overseas exhibitions remotely, including shows at the Hirshhorn Museum and Sculpture Garden, part of the Smithsonian Institution in Washington, and at Alcatraz, the former prison in San Francisco Bay.

In addition to being unable to travel outside China, he was barred from holding shows in the country. His works were also removed from group exhibitions in Shanghai last year. But last month, he was allowed to open his first solo exhibition in China, an indication that the restrictions on him had begun easing.

Mr. Ai, 57, said he planned to travel to Germany soon. He has a studio in Berlin, and his son, Ai Lao, 6, has lived in the country for the past year with the boy’s mother. He said he also planned to get a medical examination. He underwent emergency brain surgery there in 2009 after he was hit in the head by a police officer in the southwestern Chinese city of Chengdu.