• Due to the small size of their national markets, V4 countries (Czech Republic, Hungary, Poland and Slovakia) should undertake a joint implementation of the Gas Target Model that has been proposed for the European market. • A V4 level implementation would benefit from current interconnection plans and allow improved competition and liquidity, and a better exploitation of new market opportunities. • Joint V4 implementation proposals would be more likely to succeed if in line with private development interests and with other initiatives undertaken in the wider Central and Eastern Europe. • Theoretical available models span from a single price and balancing zone, to a single price zone with separate balancing areas (trading region), to market coupling and to independent connection to an external liquid market. • In practice, theoretical models are not mutually exclusive. The trading region between Austria, Czech Republic and Slovakia could be accompanied by transitional market coupling with Hungary and Poland, with a view to full integration. • Timely completion of interconnection plans and harmonised implementation of European Network Codes would underpin the process; on the contrary, single-handedly customer protection measures may hamper market development and integration. • Institutional development should be minimised and existing or market-driven forms of coordination should be preferred. Further TSO collaboration is likely, and could lead to alliances, as recently experienced by other European TSOs.