Enterprise applications are used to execute daily enterprise transactions, which are realized as business processes. These applications are complex and user unfriendly as they integrate all data and processes of the enterprise. Usability issues of enterprise application decrease business process execution efficiency, however they do not pay enough attention in the theory and industry. The goal of the doctoral thesis is to improve usability of enterprise applications using process orientation, adaptation and personalization. Current research about process adaptation, personalization and user preferences is limited within the context of enterprise applications. Therefore the naturs of user adaptive application is analysed and potential of business process personalisation is evaluated. There is developed user adaptive application modeling approach to describe adaptive features and characteristics of the application. Enterprise application which utilises business process personalisation is named as user adaptive enterprise application. In this paper is defined the concept of user adaptive enterprise application. It is compiled of 5 modules/components, which are added to the standard enterprise application. Adaptive Navigation Support (ANP) is one of those adaptive components. This paper presents the adaptation algorithm behind Adaptive Navigation Support. It personalizes business process execution within available business rules. This component is added to the prototype of real enterprise application. Afterwards usability of enterprise application is evaluated with and without Adaptive Navigation Support. The main scientific contribution of this study is: Conceptualisation of user adaptive application. Development of user adaptive application modeling approach. Development of user adaptive enterprise application concept. Evaluation of business process execution personalization possibilities. Development of adaptive algorithm behind Adaptive Navigation Support and its practical evaluation. The doctoral thesis consists of introduction, 5 chapters, conclusions, 8 appendixes, bibliography (189 titles), 47 pictures and 18 tables, a total of 132 pages.