This thesis investigates the corporate networks of Swedish property underwriters 1875-1950. During this period, networks of increasing intensity was an essential part in the organisation of the Swedish property insurance market. Corporate resource sharing allowed underwriters to accommodate the ever-changing industrialised demand for property insurance. Interlocking directorates, ownership ties and membership in collaborative organisations were the vessels of this corporate resource sharing. This study proposes a network perspective on the organisation of competition and collaboration. It finds that networks lowered firms’ cost-threshold for underwriting diversification, causing wellconnected firms to expand into new markets more easily. An essential resource to underwriters was information, and information exchange motivated several interfirm rapprochements. The driving forces for the organisational shift towards increased networking were, however, complex, and included both socioeconomic and strategic factors. Through networks of mutual resource sharing, the consolidation that appears in the industry after 1950 was preceded by a long historical process in which firms who would later merge developed measurably clustered network structures as early as in the 1910s. In the 1920s the networks already contributed to a high market concentration. Networks thereby conditioned the underwriting operation of individual firms as well as the structural evolution of the Swedish insurance market as a whole