The objective of this project was to develop and establish a database for collecting reliability and reliability-related data, for assessing the reliability of wind turbine components and subsystems and wind turbines as a whole, as well as for assessingwind turbine availability while ranking the contributions at both the component and system levels. The project resulted in a software package combining a failure database with programs for predicting WTB availability and the reliability of all thecomponents and systems, especially the safety system. The report consists of a description of the theoretical foundation of the reliability and availability analyses and of sections devoted to the development of the WTB reliability models as well as adescription of the features of the database and software developed. The project comprises analysis of WTBs NM 600/44, 600/48, 750/44 and 750/48, all of which have similar safety systems. The database was established with Microsoft Access DatabaseManagement System, the software for reliability and availability assessments was created with Visual Basic.