Background: An assessment programme, a purposeful mix of assessment activities, is necessary to achieve a complete picture of assessee competence. High quality assessment programmes exist, however, design requirements for such programmes are still unclear. We developed guidelines for design based on an earlier developed framework which identified areas to be covered. A fitness-for-purpose approach defining quality was adopted to develop and validate guidelines. Methods: First, in a brainstorm, ideas were generated, followed by structured interviews with 9 international assessment experts. Then, guidelines were fine-tuned through analysis of the interviews. Finally, validation was based on expert consensus via member checking. Results: In total 72 guidelines were developed and in this paper the most salient guidelines are discussed. The guidelines are related and grouped per layer of the framework. Some guidelines were so generic that these are applicable in any design consideration. These are: the principle of proportionality, rationales should underpin each decisions, and requirement of expertise. Logically, many guidelines focus on practical aspects of assessment. Some guidelines were found to be clear and concrete, others were less straightforward and were phrased more as issues for contemplation. Conclusions: The set of guidelines is comprehensive and not bound to a specific context or educational approach. From the fitness-for-purpose principle, guidelines are eclectic, requiring expertise judgement to use them appropriately in different contexts. Further validation studies to test practicality are required.