Assessment in the health professions is transforming. The widespread dominance of a reductionist measurement-based approach over the past 50 years is shifting towards a preference for more authentic assessment designed to promote and support learning. Assessment as a series of individual barriers, each to be surmounted, is being discarded in favour of systems of assessment designed to scaffold learner development and ensure sufficient opportunities for achievement. The intentions of these changes are to avoid the negative impacts of previous assessment approaches, such as strategic gaming, unhealthy competition and a predominance of book study, over immersion in clinical environments. However, unintended outcomes need to be considered when planning such transformative assessment change--both for those engaged in incremental evolutionary change and for those taking a more rapid or revolutionary approach. We explore three key features of programmatic assessment: longitudinal use of multiple assessment formats, a focus on assessment for learning and collation of data by attribute for decision making. We highlight the intended and possible unintended outcomes related to these features from the perspective of evolutionary and revolutionary approaches to change. We postulate that careful consideration of unintended outcomes is essential when planning significant assessment redesigns in health professional education. Anticipating unintended outcomes might also provide both the motivation and rationale to advance assessment practice into the next 50 years--particularly in the areas of enhancements in technology and collaborations across and between education providers. [ABSTRACT FROM AUTHOR]