Echocardiography was used to study the prevalence and severity of left ventricular hypertrophy in patients with established diabetic nephropathy (persistent proteinuria for at least 2 y plus severe retinopathy). Fifteen patients had mild renal impairment (serum creatinine less than 150 mumol l-1), 14 patients had moderate renal impairment (serum creatinine 150-400 mumol l-1), and 20 patients had severe renal impairment (serum creatinine greater than 400 mumol l-1). Thirty-six of the 49 (73%) were on anti-hypertensive treatment, despite which mean blood pressure was 161 +/- 25/89 +/- 9 (+/- SD) mmHg. Left ventricular hypertrophy was demonstrated in 42 of the 49 patients (85%), and increased in severity with increasing renal impairment. Interventricular septal + left ventricular posterior wall thickness was 25 +/- 3 mm in those with mild renal impairment, 28 +/- 6 mm in those with moderate renal impairment and 30 +/- 4 mm in those with severe renal impairment. The most severe left ventricular hypertrophy was seen in the Afro-Caribbean patients. Left ventricular hypertrophy was present even in those with marginally raised blood pressure and was related to age and serum creatinine but not to present blood pressure or duration of proteinuria.