An understanding of the hormonal basis of normal growth and development, including the changes occurring at puberty, is important foundation knowledge for contemporary medical practice in most fields of medicine. A quiz, testing the important physiological concepts of growth and puberty, was designed using the format of the well-known television game "Who Wants to Be a Millionaire." An evaluation of this formative assessment activity revealed that a cohort of first-year undergraduate medical students valued learning with peers in an enjoyable, interactive environment, where they were able to admit to uncertainties and clarify answers. It also showed that making an educational activity fun need not detract from the focus of giving feedback on learning. Formative assessment, known to produce learning gains in a range of educational settings, is an important activity in contemporary medical education. With a greater emphasis on self-directed learning and less well-defined curriculum boundaries, feedback helps students to understand and apply the important physiological concepts that underpin the practice of medicine. (Contains 4 tables.)