Under South African common law, an interest rate is not usurious merely because it is high or exceeds rates prescribed in consumer protection legislation. To establish usury at common law, a party must prove extortion, oppression or something akin to fraud. The common law principle is not inconsistent with the Constitution; rather, it promotes constitutional values of contractual autonomy, freedom, dignity and legal certainty. Courts should not interfere with freely negotiated contracts between parties dealing at arm's length merely because a judge subjectively considers the interest rate unfair. All circumstances must be considered including: the ordinary rate for similar transactions, security offered, risk involved, loan period, amount lent, relative positions of parties, whether terms were negotiated, whether independent advice was obtained, and the commercial sophistication of the borrower. The onus rests on the party challenging the interest rate to establish the factual basis for finding usury.