Prevalence of Isolated Systolic Hypertension (ISH) defined as systolic blood pressure greater than 160 mmHg and diastolic blood pressure less than 90 mmHg was studied in a population of 148 patients treated by hemodialysis whose 80 had undergone ambulatory blood pressure (ABP) recording during the interdialytic period. All patients were treated 3 times 4 hours a week. ABP was recorded for 48 hours between two sessions of hemodialysis using a Delmar Avionic Presurometer (PIV). Prevalence of ISH was 12.5%, while that of systolic-diastolic hypertension (SDH) was 15%. Average age at the time of the study was respectively 59 +/- 13 yrs ISH and 49 +/- 11 yrs SDH (p less than 0.01) while that of patients with normal blood pressure (N) was 57 +/- 10 yrs. Mean duration of HD treatment was no different between groups: 5.3 +/- 3.5 yrs ISH, 5.0 +/- 4.2 yrs SDH and 5.0 +/- 4.3 yrs N. Causes of end-stage renal disease were similar in each group. All patients with ISH and SDH and 42% of N pts were receiving antihypertensive treatment at the time of ABP recording. Finally, level of anemia and percentage of patients treated by EPO were similar in each group.(ABSTRACT TRUNCATED AT 250 WORDS)