The present analysis deals with two types of cross border co-operations between business firms: on the one hand the bi-national horizontal groups (type Shell, Unilever). This form of co-operation allows firms to fully integrate without loosing their legal identity. Proposals are made to develop a "default scheme" which firms could adapt. The second subject deals with cross-border take-over: issues of conflicts of laws are numerous. The rule of the market where the target's shares are traded, is dominant, but incidentally account will have to be taken of the jurisdiction of the target company, if registered in another state. The 13th directive contains useful connecting factors. Published in: N. HORN (Ed.), Cross-Border Mergers and Acquisitions and the Law. Studies in Transnational Economic Law, vol. 15, 2001, p. 63-89, Kluwer Law Int.