Besides an overall increase in blood pressure, hemodialysis patients have marked disturbances in interdialytic ambulatory blood pressure pattern that is characterized by blunted circadian amplitude and a steady rise in blood pressure between dialysis treatments. The pathophysiology of this abnormal blood pressure profile is poorly understood. We hypothesized that the circadian amplitude, the interdialytic increase (linear trend), and the average level of blood pressure (the intercept) is related to the extent of arterial stiffening and the degree of accumulation of salt and water between dialysis. Using a generalized cosinor model, we simultaneously compared the impact of interdialytic weight gain and echo-Doppler measured aortic pulse wave velocity on the mean level of blood pressure, linear changes over the interdialytic interval and oscillatory changes in blood pressure. In a cross-sectional analysis from 11833 blood pressure measurements from 125 long-term hemodialysis patients, we found that aortic pulse wave velocity and interdialytic weight gain had a substantial impact on interdialytic ambulatory blood pressure level, trends and rhythms. Arterial stiffness was associated with an overall increase in the level (intercept) of systolic, diastolic and pulse pressure. Interdialytic weight gain, on the other hand, was associated with interdialytic increase (linear trend) in blood pressure. The circadian amplitude was blunted by increments in either arterial stiffness or interdialytic weight gain. Since patterns of ambulatory arterial blood pressure are related to cardiovascular risk factors such as interdialytic weight gain and increased arterial stiffness, the pattern of ambulatory BP recordings may also be of prognostic significance in hemodialysis patients.