Vollertsen practiced medicine in North Korea from 1999 to 2001 with the Cap Anamur Committee, a non-governmental cooperation organization. In August 1999, he and Francois Large, another aid worker, donated their skin to Pak Jong Thae, a tractor factory worker in Haeju, South Hwanghae, who had suffered burns over three-quarters of his body and underwent three skin grafting operations. In recognition of his contribution, Vollertsen received the official Democratic People's Republic of Korea's Friendship Medal for his humanitarian assistance later that same month, in a ceremony attended by Supreme People's Assembly vice-president Yang Hyong Sop. He was also given a pass that allowed him to travel through the country freely, which was very unusual for a foreigner.
As he traveled in his capacity as an emergency physician, tending to the illnesses and injuries of common North Koreans in the countryside, he struggled with a nearly non-existent healthcare system, abject poverty and growing proof of a network of Prisons in North Korea that enforced the flow of wealth from the citizenry to the Pyongyang-based Korean People's Army and the Workers' Party of Korea which was then headed by Kim Jong-il. Using smuggled cameras, he obtained photos and films of flagrant, large-scale Human rights violations in North Korea. In particular, mass starvation was used as a tool of political control. He began collecting evidence of abuses, which he passed to a visiting United States Congress man, an act for which he was put under surveillance. Despite this Vollertsen continued to speak out against the North Korean government, which soon lost patience and forced him to leave North Korea in January 2001. Soon after returning home, he gave an interview about his experiences in North Korea, which the North Korean government denounced.
The North Korean government has portrayed him as a dishonest media manipulator who is suffering from mental instability. His wife, reacting to his decision to stay in South Korea as an anti-Kim activist, divorced him and is raising their children with a partner. "My wife blamed me for not taking care of my family. She said my vision, my goals, my projects, were worth much more to me. And afterwards, I realised she was right. I do not want to sacrifice my family. But I know my wife and her partner are taking care of my children, and that they are safe and healthy. But the North Korean children are not", said Vollertsen in 2003.
- Vollertsen, Norbert (2004). Inside North Korea: Diary of a Mad Place. San Francisco: Encounter Books. ISBN 978-1-893554-87-0.
- "Germans donate their skin to Korean patient". Korean Central News Agency. 1999-08-05. Retrieved 2007-07-10.
- "DPRK Friendship Medal awarded to Germans". Korean Central News Agency. 1999-08-23. Retrieved 2007-07-10.
- Edmonds, David (2003-04-23). "Westerner's help for N Korean refugees". BBC News. Retrieved 2007-07-10.
- "Spokesman for DPRK FDRC on letter from German "Cap Anamur" Committee". Korean Central News Agency. 2001-01-16. Retrieved 2007-07-10.
- Koehler, Robert (2006-09-25). "Things Getting Darker for Vollertson". The Marmot's Hole. Retrieved 2007-07-09.
- Vollertson, Norbert (2004), Inside North Korea: Diary of a Mad Place, San Francisco: Encounter Books, ISBN 1-893554-87-2, OCLC 226117315
- 瀬木碧 [Midori Segi] (2001), 北朝鮮を知りすぎた医者国境からの報告 [The doctor who knew too much about North Korea: A report from inside the borders], 草思社 [Sōshisha], ISBN 4-7942-1090-6, OCLC 48952380, JPNO 20208614
- Norbert Vollertsen on the Institute for Corean-American Studies website.
- Interview with the blog One Free Korea, October 28, 2005.
- Lecture transcript, October 14, 2003.
- "Eyewitness to the Axis of Evil", Good News Magazine, May/June 2002 issue.
- "Diary of a Mad Place", Time Asia, January 22, 2001.
- "For the Masses, 'Nothing Has Changed,' Expelled Doctor Asserts", The International Herald Tribune, January 9, 2001.