Principle of "stability of contracts" has been recognized by most legal systems. Autonomy of contracts and their subordination from the common intents of the parties, require the content of contracts to be always binding upon the parties. However, the scope of the principle is not absolute. For in certain circumstances, noncompliance with the principle has been accepted both at national and international levels. Thus, jurists have always tried to replace the applicability of the principle pacta sunt servanda with adjustment or abrogation of contracts, if fundamental changes of circumstances disturb the contractual adjustment between the parties making implementation of obligations too difficult. Doctrine of rebus sic stantibus is applicable both to national and international long lasting obligations. In international law resort to the doctrine is an exception to the principle of pacta sunt servanda. The Iranian legal system has approached the issue carefully and consequently, making adjustment in contracts due to fundamental changes in circumstances of concluding time of contracts is a controversial matter. Nevertheless, it seems that the principle can exceptionally be accepted in the Iranian private law on three grounds of "sudden deception" (ghabne hades), "rule of hardship" (Osr VA Haraj) and "theory of interpretation of parties intents".