Dr. Hildebrant Gurlitt subjected his 208-piece art collection to scrutiny by the U.S. Army in 1945 and filed the necessary paperwork for its return five years later, according to information provided by The Central Registry of Information on Looted Cultural Property 1933-1945's Lootedart.com, "Hildebrand Gurlitt: Allied Interrogation June 1945; List of Artworks in his Collection Returned to him by the Allies in 1950 and the Related Documentation":

On 8-10 June 1945 Hildebrand Gurlitt was interrogated at Aschback by Lieutenant Dwight McKay of the US Third Army about his activities as a Nazi art dealer. The statement resulting from that interrogation, in which, inter alia, he denied ever handling seized art in France, and in which he lists some of the sources of acquisition of the works in the collection, is available here.

After my dismissal in Zwickau (1930) I gave lessons of history of art in the Academy of Applied Art in Dresden, published a book about Kathe Kollwitz (a then famous German woman-artist) public debates against Nazi-art and wrote articles for the Vossische and Frankfurter Zeitung. 

1931 I was called to Hamburg as director of the Kunstverein. I arranged exhibitions, lectures about modern art, unpopular with the Nazi movement. Made an exhibition of modern English art, one of modern German art in Sweden, made trips to England and Scandinavia. Was dismissed in 1933 on account of my Anti-Nazi feelings. Got denounced because I had the flagpole of the Gallery sawed off, in this way avoiding the showing of the swastica flag.

I had given to me the photos of paintings and mostly Dr. Voss bought them wihtout having seen them, entirely on the strength of my descriptions. Any force whatsoever was not used. If Dr. Voss thought the pictures to (sic) expensive, he did not buy them.

How it was with pictures from Jewish collections 

As I heard, the Jewish owned art treasures in France were seized by a law, but which I have never seen with my eyes. I know that the German Ambassador used a Baroque Writing desk which came from the Rothschild collection. I also saw marvellous Franch drawings from the 18th century in the rooms of the German Embassy, which were said to come from the same source. It was told to me, that there existed in paris a palace in which the Jewish art possessions were collected and where they were divided among the different officials. I never went to this building. They told me that a certain Mr. Lohse, who was acting for Goring, was the chief of this house. I avoided meeting this man and met him only once in an exhibition without my intention. I always avoided to meet high Nazi-Officials in Paris. I was only once to a large reception in the embassy together with hundreds of people. There was rumor that the Gestapo bought under pressure, paintings from private or dealers, which I heard very often, but I never could prove it or even get reliable information, as I otherwise should have gone after such an accusation and would have informed Prof. Voss privately. I did notice indeed that I was not shown many pictures, which were reserved for other dealers.

According to Dr. Gurlitt, he made 10 trips to Paris between the summer 1941 and June 1944: 'In total I acquired about 200 paintings in France and have given them to museums.' His 'income increased steadily, because I was very active and developed my business more and more.' As to his 'personal fortunes' he includes 'the safe deposit box of the Dresdner Bank' of 'silver and the paintings of my father and also the pictures of my deceased sister'. He denies having any paintings from the Dresden Museum in his possession: 'All pictures I brought with me from Saxonia are the personal property of my family or myself. I have never in the house pictures of other owners. '

I was told, that I was a poor man before the Nazis came and that I now have money and a whole truck-load of paintings. To that I have to reply, that I was well off as director of the Kunstverein Hamburg with a monthly salary of 600 R.M. and a commission on every picture sold. I had an apartment of 12 rooms, a very large library and a nice art collection. I had a good future ahead of me and would inherit one day the house of my mother in Dresden, with the library and collections of my father, his personal fortune and the contents of 14 rooms filled with antique furniture. Dismissed by the Nazis, I became an art dealer, very much against my purely scientific intentions.

In the list of 'Contents of opened boxes in Castle Aschback belonging to H. Gurlitt' it is written that he purchased a Courbet from Engel in Paris for 150,000 French francs; that a Liebermann was 'from the possession of my father who bought it in Rome'; a Picasso bought from the artist in Paris in 1942 for 60,000 French francs; a Chagall, 'old possession of my sister, who was a pupil of her'(?); a Dix from Berlin in 1934; and a Nolde, 'gift of the artist to me'.

Here's a link to the list of works returned to Gurlitt in 1950 (also published in The New York Times here).

Lootedart.com notes that 'on the list is the MaxBeckmann 'Lion Tamer' sold by Cornelius Gurlitt at Lempertz Cologne in 2011 (previously owned by Alfred Flechtheim with claims settled prior to the auction house sale). Patricia Cohen writes about this in The New York Times' "Documents Reveal How Looted Nazi Art Was Restored to Dealer".

On another note, Mail Online ran the story "Can the weirdo who hid £1bn of Nazi art solve the mystery of the Tsar's lost treasure trove" which includes statements from Cornelius Gurlitt's estranged cousin.