Insurers are realizing that big data has the potential to create competitive advantage. There is a gold mine of information residing across the large volumes of data available in multiple sources and disparate formats, if only it can be efficiently mined to support key operational decisions and improve the customer experience. Commercial risk assessment is data intensive and ripe for the incorporation of real-time external data. In this paper, we explore the ways commercial insurers can gain accurate and comprehensive risk assessments when underwriting policies by using big data.