ETL tools are part of Business Intelligence systems. They allow to integrate the data from different sources using dedicated drivers. Thereby these tools can be connected with distinct IT systems (e.g. ERP, CRM), data bases and external files (e.g. Excel and CSV files). When it is necessary to integrate the data from sources which don’t have predefined drivers, it is possible to use ODBC or OLE DB interface. ETL tool selection is a very important part of Business Intelligence system designing. It is worth to benefit from specialists’ experience who have done a lot of implementations and know this type of tools.