Abstract A new edition of the FIDIC Red Book is under discussion. It is an issue whether this edition should be based on the current edition or there should be a complete break with tradition in favour of a contract based on a new philosophy such as that of the NEC, which is reported to be used in many countries in circumstances in which the Red Book would otherwise have been used. This article compares the two contracts on the way they deal with site conditions issues. The comparison is on equity and clarity in risk allocation, adequacy of contractual procedures for dealing with unforeseeable conditions encountered, effectiveness of contractual machinery for dispute resolution, and compliance with reported new developments in successful contractual practices in underground construction.