Glomerulonephritis (GN) is a group of conditions characterised by inflammation in the filtering units of the kidney which may be 'primary'; secondary to drugs, infections or tumours; or the presenting feature of systemic disease. GN is treatable, causes significant morbidity and mortality, and is a potentially preventable cause of renal failure and cardiovascular risk. It can only be precisely identified and characterised by renal biopsy which is usually undertaken in specialist nephrology centres. The role of the non-specialist is to know when and how urgently a patient should be referred to such a centre. This review aims to provide guidance on when to suspect GN, how to investigate this possibility and when to refer for further investigation. Clinically urgent situations are highlighted. The importance of urinary abnormalities, particularly proteinuria (even if aysmptomatic and only detected on routine screening) is emphasised. Earlier recognition of GN will improve patient outcomes.