Contract sales organisations have a number of advantages for pharmaceutical companies large and small, and they manage a growing proportion of the sales in the sector. (The CSO market in pharma was $2.5bn in 2006 and forecasted to exceed $5bn by 2011.) Their use can, however, still be a very confidential matter. There is relatively little academic exploration of the relationship between pharmaceutical companies, their CSOs and health professionals as their mutual customers, so this paper draws on trade sources of information, news and comment, in order to offer a view of the developing business model. This is an exploratory paper, intended to give readers an overview of the history of outsourcing and the changing role of CSOs. It concludes that while CSOs have a history of providing tactical services, their flexibility and speed can also help clients to achieve strategic change in difficult market conditions. Strategic partnering is emerging as their future.