The exchanges were written by crimelord Reggie Kray while he served a life sentence in prison, to Carol Clerk, the ghost writer of his autobiography.
Kray ran a huge crime empire across the east end of London in the 1950s and 60s, alongside his brother, Ronnie.
The letters, which will be sold at McTear's Auctioneers, are valued at between £10,000 and £15,000.
McTear's managing director Brian Clements said: "Ronnie and Reggie Kray's names are synonymous with gangland life. Anything associated with the pair always attracts interest.
"We do see Kray items coming to auction but we have never seen anything on this scale going under the hammer.
"When Reggie met his ghost writer in prison they were not allowed to take notes so all Reggie's thoughts and ideas had to be put in the form of letters after the meetings."
Victoria Irvine, a valuer at McTear's, said: "They're fascinating. The details that Reggie Kray revealed to his ghost writer throughout the 1980s and the early 90s, which all culminated in his autobiography, 'Born Fighter', make for a very interesting read.
"It's a snippet of the life of someone who was very important historically. We have sold letters before by Charles Manson and they did very well at auction, which is why I believe these letters have come to Scotland."
The Kray brothers, were sentenced to life imprisonment in 1969 for their involvement in armed robberies, arson, protection rackets, assaults, and the murders of Jack "The Hat" McVitie and George Cornell.
Ronnie died in Broadmoor Hospital in 1995 while Reggie died from cancer in October 2000, eight weeks after he was released from his term on compassionate grounds.
