In recent years financial conglomerates have been established throughout Europe. This horizontal diversification has attracted a great deal of attention in the banking and insurance sector, as well as alarming the supervisory authorities and the European Commission. This study analyzes different sets of definitions of financial conglomerates, groups, consolidation criteria, and tests the practical effects of these definitions on the basis of a detailed relational database. It also examines the benefits of financial conglomerates as well as the differences in regulation of the solvency requirements for banks, insurance companies and investment firms in order to look for a possible approach for calculating the necessary level of solvency for financial conglomerates.