While many studies have been devoted to capital accumulation and rate of profit, the article empirically characterises the financialization at the level of firms' liability, i.e. at the level of debt and equity. In particular, the determinants of non financial firms' indebtedness and equity issuing will be analysed econometrically. The theoretical framework is mainly Post-Keynesian, with the founding role played by Minsky (1986) and with Stock Flow Consistent models proposed by Lavoie and Godley (2001), Godley and Lavoie (2007), Taylor (2004) and Dos Santos and Zezza (2008 )with their analysis of interactions between financial variables and investment. The article is based on the flow of funds accounts of INSEE which provide coherent data in flows and stocks over the period 1978-2007. Thanks to a precise account of financial assets and liabilities and capital gains, these data allow to implement a rigorous analysis of firms' financial behaviour at the macroeconomic level.