The effect of eating on BP during hemodialysis was examined in nine nondiabetic end-stage renal disease (ESRD) patients. A standard meal was given during 62 of 125 dialysis treatments in a prospectively controlled study. Diastolic (P = 0.01) and mean (P = 0.03) BPs fell significantly faster in the 45-minute postprandial period in the fed treatments compared with equivalent times in the fasting treatments. In this period, symptomatic hypotension occurred 13 times in five patients fed during dialysis compared with two episodes in one patient while fasting (P less than 0.05). Consumption of meals during hemodialysis should be avoided in patients at risk for hypotension during treatment.