The doctrine of illegality and immorality, pactum turpe, has been questioned by several scholars lately. The fundamental problem is that we live in an increasingly multicultural society governed by a postmodernist paradigm where no objective or universal values can or should be taken for granted. Within the framework of such a societal structure it can, on the face of it, seem hard to establish any moral values that can constitute the basis of pactum turpe. The purpose of this thesis is to analyse the conflict of interest between the principle of freedom of con- tract and pactum turpe. This essentially entails answering how such an antique legal principle as pactum turpe can be used in a postmodern context. More concretely, the following questions will be examined: Is pactum turpe an obsolete doctrine? With which methods can one deduce immorality? Which typical cases does pactum turpe cover? What method has primacy when deducing immorality? The first question was answered in the following way. Pactum turpe is not an obsolete doctrine, on the contrary, it fills many important functions. A historical inquiry shows that there has always been a need for pactum turpe since the roman times. Furthermore, all modern legal systems have a doctrine of illegality and immorality in order to declare certain immoral contracts void or to dismiss actions founded upon such contracts. The commodification tendencies, the shift of emphasis in the freedom and rights discourse and the expanding multicultural society all point to the fact that more cases regarding the (im)morality of contracts will have to be solved by the courts. As of now there is no legal mechanism that can replace the procedural functions of pactum turpe; neither its substantial scope of application. The second question was answered in the following way. Four different methods with which immorality can be established have been found: the intuitive method, the reductionist method, the holistic method and the pragmatic method. The third question was answered in the following way. The typical cases covered by pactum turpe are contracts in breach of law; contracts regarding family relations or personal integrity; agreements on tax evasion; gambling contracts; and agreements on circumvention of law. This is not a closed categorisation which the application of pactum turpe is limited to. New situations may become commonalities as the society evolves and new problems become relevant. The fourth question was answered in the following way. An analysis of the typical cases shows that the Supreme Court favours the pragmatic method in order to deduce immorality. Case law – especially NJA 1955 s. 544, NJA 1989 s. 768, NJA 1997 s. 93, NJA 2002 s. 322, NJA 2008 s. 861 and NJA 2019 s. 504 – suggests that a nuanced approach has primacy. The holistic method has only been applied in occasional cases, for example RH 2004:41. It seems like the intuitive method was common in earlier times, especially in the lower courts. The reductionist method has not been used by courts at all; this is because it is not practical for courts to use questionnaires and statistics in order to de- cide the immorality of a contract.