The aim of the article is to analyse selected issues relating to the statutory provisions and contractual terms which allow to amend or terminate a contract in the event of a change in circumstances occurred after the conclusion of the contract. Many provisions of the Polish Civil Code grant in such a case one of the parties the right to unilaterally amend or ter-minate the contract by its declaration of will or a right to demand for a change or dissolving the contract by the court. The parties may also agree the specific terms in the contract which allow adopting their contractual relation to new circumstances. If a party affected by change of circumstances exercises its right to modify the contract it should be considered a problem of how the interests of the other party should be protected. Particularly the question arises whether the statute or the contract grants such a party the right to terminate the contract.