The use of external business coaches to improve the performance and competence of employees is increasing dramatically. However, there is still little empirical research attesting to its effectiveness in achieving business goals, and there is no universally accepted way of evaluating its added value to the individual or the organisation. This study takes a multi-dimensional approach to reviewing the published literature on the tangible benefits of business coaching combined with the more established processes of training evaluation and business results measurement. The study goes on to identify, via a case study, how a group of corporate purchasers select and measure the effectiveness of external business coaches. Data is also obtained from a large-scale national survey of people receiving coaching in a variety of business contexts. A grounded theory methodology is applied to the data to identify what factors the key stakeholders perceive to be important in deciding if a business coaching relationship is successful. These factors are then used to develop a generic and holistic framework and associated benefits model that is proposed as relevant to both corporate purchasers and external suppliers of business coaching.