Hypertension is common in chronic hemodialysis (HD) patients. However, its prevalence and determinants have not been studied in a large HD population. We analyzed the database of the Japanese Society for Dialysis Therapy (JSDT) registry, which conducts an annual survey of chronic dialysis patients throughout Japan. We compiled those who were on HD three-times per week and aged 20 years and over at the end of 2000 (JSDT standard analysis file 001). Hypertension was defined as predialysis systolic blood pressure (SBP) > or =140 mm Hg or predialysis diastolic blood pressure (DBP) > or =90 mm Hg. Adjusted odds ratios (95% confidence interval) for the determinants of hypertension were calculated by the multivariate logistic regression analysis. A total of 65 393 people (men, 60.2%; mean age +/- SD, 60.9 +/- 12.8 years; and mean duration of HD +/- SD, 95.3 +/- 74.0 months) were studied. Mean +/- SD levels of SBP and DBP were 154.9 +/- 23.8 mm Hg and 80.5 +/- 13.7 mm Hg before the HD session. Hypertension was noted in 77.5% of patients. Prescription of antihypertensive drugs and erythropoietin was made to 60.7% and 82.0% of patients, respectively. Both SBP and DBP were higher in those who were prescribed antihypertensive drugs (mean, 160.4/81.9 mm Hg), than those without drugs (mean, 146.9/78.5 mm Hg) (in both cases P < 0.0001). Hypertension was positively associated with men (adjusted odds ratio (OR), 1.258; 95% confidence interval (CI), 1.188-1.333; P < 0.0001), age (OR, 1.004; CI, 1.001-1.006; P < 0.01), duration of HD (OR, 0.769; CI, 0.728-0.812; P < 0.0001), serum albumin (OR, 1.369; CI, 1.286-1.458; P < 0.0001), and change in body weight by dialysis session (DeltaBW) (OR, 1.176; CI, 1.159-1.194; P < 0.0001), and was negatively associated with Kt/V (OR, 0.600; CI, 0.543-0.664; P < 0.0001), and hematocrit (OR, 0.964; CI, 0.959-0.970; P < 0.0001). The distribution of DeltaBW was normal in shape and in about 22% of patients the range was from 4.0% to 4.9%. There was a significant positive relationship between the prevalence of hypertension and DeltaBW (R(2) = 0.8549). The higher the DeltaBW, the more the prescription rate of antihypertensive drugs increased (R(2) = 0.9102). Results showed that the prevalence of hypertension was significantly associated with volume excess and serum levels of albumin, calcium, and phosphorous in chronic HD patients. Despite the high prescription rate of antihypertensive drugs, control of blood pressure remains unsatisfactory.