This Viva tested knowledge of renal physiology and pharmacology. It began by asking what the normal Glomerular Filtration Rate (GFR) is and what the determinants of GFR are. It also explored knowledge of glomerular-tubular feedback, the counter current system and diuretics. Although most candidates had a good knowledge of GFR and its determinants, fewer were as confident to recall the actual values or to apply that physiology to scenarios like hypovolaemia. Some candidates struggled to explain the counter current mechanism, in particular the “multiplier” effect. Mechanism of action of diuretics was well answered.