The urinary erythrocyte morphology of 120 patients with haematuria of diagnosed cause (41 glomerular, 79 non-glomerular) was examined by red cell analyser (RCA) and by phase contrast microscopy (PCM). By RCA three distinct ranges of modal erythrocyte cell volume (ECV) were observed. The modal ECVs in glomerular haematuria (35–50 fl) were significantly lower than in non-glomerular haematuria (65–148 fl) and both were clearly distinct from ‘debris patterns’ (12–33 fl). In duplicate specimens very similar ECVs were observed before and after centrifugation and after storage for up to 15 h. There was no correlation between the modal urinary ECV and the urinary specific gravity or the peripheral venous ECV. The source of the haematuria (glomerular or non-glomerular) was identified correctly by RCA (PCM) in 100% (60%), 68% (71%) and 22% (39%), respectively, of patients with macroscopic, 3 + microscopic and 1–2+ microscopic haematuria. In no patient was the haematuria localised incorrectly by RCA as compared with 10% incorrect localisation by PCM. RCA and PCM are complementary non-invase tests and both should be performed whenever possible in the investigation of haematuria.