A Polish man living in Germany spent five years with a bullet in the back of his head having forgotten he was shot because he was drunk when it happened.
Police in the western city of Bochum said doctors had found a .22-calibre round after the 35-year-old asked them to remove what he thought was a cyst.
They said the man recalled receiving a blow to the head around midnight at a New Year's Eve party "in 2004 or 2005".
It is thought it might have been a stray bullet fired in celebration.
"It may have been a shot fired up in the air which entered his head on the way down," a police spokesman told reporters on Tuesday.
"He told us he remembered having a sore head, but that he wasn't really one for going to the doctor."
The man, who has lived in Germany for several years, is expected to be released from hospital later this week. The bullet, which was lodged in his scalp and did not penetrate his skull, was removed on Friday.