Make a polite but friendly formal request in writing and give a deadline by which you would like the money repaid. Stress that you would like to deal with the matter amicably but the money is important to you and you now need for it. Say you value your friendship and would prefer not to have to take legal action which would damage your relationship but the sum of money is so large that you can't afford to write it offf. If that doesn't do the trick I'm afraid you may have to sue. When you loaned the money did you get anything in writing? If it was less than six years ago and you wrote a cheque for the loan, you bank may still have a record of it via your bank statement. They may even have a copy of your cheque in their archives even though banks no longer return cheques to their customers. Contact them immediately to get this evidence. You may need it if you are forced to sue. Good luck and hope you see your money back soon. And be very wary about loaning money again, although you've probably already come to that conclusion yourself!