Saving is an strategic magnitude in any country's economy,to the point that it is the main source to finance fixed capital investment on which economic development must be based.The understanding of the development of national savings is, therefore, essential to be able to follow the economic changes. The contribution to saving of the institutional sectors (households, companies and businesses, and public administrations) is also necessary to explain the causes for the leads andlags in any economy. In Spain's case, it is also relevant to know the contribution to the national saving of the regions of each of the seventeen autonomous communities.This present paper includes as a novelty theassessment, for the whole of Spain, of the financial saving as obtained from the Financial Accounts of the Bank of Spain, as well as the volume of the financial assets and liabilities of the institutional sectors. The aim of this paper is to verify whether the interrelation admitted between saving and investment in the macroeconomic framework is also true at corporate level. If this is so, the determinant factors of investmenwould be economic as well as financial, and this would be a test of the imperfection of the financial market and the interdependence between corporate investmentand financing decisions. By using a data-base from the Central de Balances in the Bank of Spain, referring to the period 1990-1995 and based on size distributionof firms, such interrelation can be observed as well as the especial incidence of the following factors on corporate investment: asset profitablility and the volume of business, amongst the economic factors; and theleverage level and its bank credit component, as wellas the financially sustainable growth; amongst the financial.