This thesis aspires to advance understanding of how start-up firms’ and small and medium sized firms’(SMEs) network relationships affect acquisition of financing and information necessary to achieve firmbusiness development through the exchange in business relationships. It contributes to research on socialstructure by clarifying how network relationships that facilitate exchange have a positive effect on firmbusiness development, defined as subjective and objective enhancement of firm performance. The empirical setting consists of case studies in entrepreneurial start-up firms and of quantitative researchin SMEs. The findings show that in the start-up phase of firm development, network relationships that areembedded in social attachment and shared cognitive schemes constitute means to acquire informationcontaining referrals to new business partners, thus affecting the structural development of start-ups firms’business network. Findings further show that relationships to banks are important in order to fund thisstructural development. The thesis also shows the effects of banks, as institutional actors, on SMEs’investments in international business relationships and the effects of such investments on SMEs’ businessdevelopment. It is shown that relationships to domestic and local banks in different ways affect SMEs’specific investments in international business relationships. A local bank relationship decreases the SME’srelationship specific investments, while a domestic bank relationship increases relationship specificinvestments. There is however an indirect positive effect of a local bank relationship on the SME’srelationship specific investments, mediated by a positive effect of the SME’s relationships to other localinstitutional actors. The results further show that increases in relationship specific investments promoteSMEs’ business development. Findings made in this thesis also show that institutions, experiencedthrough interaction in the international business relationship, positively affect relationship specificinvestments and the performance enhancement of such investments. A general conclusion drawn fromthe findings presented in this thesis is the relevance of a type of actor - actors that facilitate exchangesamong firms and their business partners who are, or wish to be, independent - to the businessdevelopment of start-ups and SMEs. This thesis challenges banks to increase cognitive alignment with customers of start-up firms and toconsider corporate customers in view of their business relationships and network structure. Theseapproaches are suggested to facilitate bank’s assessment of firm creditworthiness. / <p>QC 20100722</p>