E-learning is increasingly being adopted as a routine instructional media, and has moved from a niche solution in the defence and aerospace industries, to one that is adopted across the vast majority of industries and within education worldwide. E-learning is not however suited for all types of learning outcome or for all instructional situations. In this paper we describe a new instructional media selection model which enables the assessment of suitability of e-learning to a particular learning outcome. Following a review of media selection theory, seven key decision areas were identified. These consideration areas are; Learning Task, Media Attributes, Grouping Strategy, Learning Context, Learner Characteristics, Instructional Management and Cost Effectiveness. The paper focuses on the identification of the key decision factors for selecting e-learning and the development of detailed guidance within each decision area to enable an assessment of suitability of e-learning to be made. Finally we outline the dependencies and interactions between decision areas to illustrate the compromises inherent in instructional media selection, and to produce a model of these inter-relationships. (Authors' abstract)