The paper, a substantially shortened version of the national report prepared for the congress of the International Academy of Comparative Law in 2018, analyses processes of formal and informal constitutional amendment in the Czech Republic. After outlining the basic relevant characteristics of the Czech constitutional amendment in the Czech Republic. After outlining the basic relevant characteristics of the Czech constitution (poly-legality, rigidity, etc.), the paper examines procedural issues of formal constitutional amendment and studies further requirements regarding such constitutional changes, esp. the role of Art. 9 of the Consttitution Several varieties of informal constitutional changes are then briefly presented. The paper assesses the current situation regarding processes of both formal and informal constitutional changes, finding the formal requirements prescribed for a constitutional amendment as sufficient for the relative stability of the constitutional system, being neither extremely strict not benevolent. The paper also points out several open questions regarding the practical application of the unamendability provision of Art. 9(2) of the Constitution in relation to potential constitutional amendments adopted through a constitutional referendum. Finally, the paper deals with the issue of how formal constitutional amendments can impact upon informal constitutional changes, using the example of the introduction of the direct election of the President of the Republic in 2012.