Left ventricular hypertrophy (LVH) is known to be a strong predictor of cardiovascular death in dialysis patients, but the mediators for its development remain to be clarified. In the non-renal population risk factors for LVH differ between the genders. We therefore studied 46 non-diabetic patients (26 male, 19 female) on maintenance hemodialysis (n = 25) or continuous ambulatory peritoneal dialysis (CAPD) (n = 20) all free from clinically evident cardiac disease, who underwent 48-hour ambulatory blood pressure (BP) monitoring, 2-D and M-mode echocardiography for left ventricular mass index (LVMI) and bloods for hemoglobin, parathyroid hormone (PTH), urea and electrolytes and liver function tests. Thirty-two out of 45 patients were taking antihypertensive drugs at the time of the study. The mean 48-hour BP was 135 +/- 19/83 +/- 13 mmHg and the mean LVMI was 144 +/- 50 g/m2. LVH (LVMI > 131 g/m2 men, > 100 g/m2 women) was present with equal frequency in both sexes: men 72% (18/25) and women 68% (13/19). Simple regression analysis showed that LVMI was correlated with 48-hour pulse pressure (r = 0.52, p < 0.00033), 48-hour systolic BP (r = 0.37, p < 0.05), PTH (r = 0.31, p < 0.04) and inversely with serum calcium (r = -0.29, p < 0.05) and hemoglobin (r = -0.33, p < 0.03). However, on multiple regression analysis pulse pressure (R2 = 28.7%), day systolic BP (R2 = 15.4%) and 48-hour systolic BP (R2 = 14.1%) were the only variables linked to LVMI. When the patients were split by gender, stepwise linear regression in the men showed a highly significant relationship between LVMI and pulse pressure (R2 = 37.1%) which was stronger at nighttime (R2 = 42.6%), but in females this was not apparent (R2 = 4.39%) and indeed no variable was linked to LVMI. Our study confirms that LVH is not only prevalent in dialysis patients but is present with equal frequency in both sexes. However the determinants of its development are different for each gender. In males pulse pressure, and therefore by implication vascular compliance, is important but in females, other unidentified factors predominate.