For many decades, revenue performance in pharmaceutical companies seemed to be directly correlated to the number of sales representatives employed. Now the `arms race' is over, and the number of sales representatives in the pharmaceutical sector in the United Kingdom is decreasing. Sales Directors in major pharmaceutical companies are rationalising internal sales resource strategically and working with contract sales organisations (CSOs) to provide coverage for campaigns. Smaller players, who are often experiencing high growth rates, also engage with contract sales organisations and are more likely to ask them to manage multiple relationships with the NHS. Previous research about the use of contract sales organisations has predominantly been generated in the United States, where `manufacturers' representatives' generate a significant minority of revenue in B2B markets. Use of `reps' or similar organisations appears to be increasing in the United States, and the variety of contract sales organisations and their tasks is also developing. Earlier research has identified reasons why US manufacturers use `reps' and how they are usually deployed. Building on that body of knowledge, this paper explores the factors that are driving successful deployment of CSOs in the UK pharmaceutical sector. It is based on interviews with senior decision-makers in 12 companies whose combined market share represents about one third of UK healthcare spend.