The effect of a reduction in dialysate temperature on BP during hemodialysis was studied in seven patients with end-stage renal disease suffering frequently from intradialytic hypotension. Each patient received six dialyses using 34.4 degrees C dialysate. These treatments were preceded (six dialyses) and also followed (six dialyses) by control periods using a 36.7 degrees C bath. Symptomatic hypotension was defined as systolic BP below 100 mm Hg associated with typical symptoms of hypotension requiring treatment with intravenous (IV) fluid. Cool dialysate reduced the frequency of symptomatic hypotension from 0.58 to 0.05 episodes per dialysis (P = less than 0.016). In addition, the rate of fall of mean BP during treatment was substantially slowed with the reduction in dialysate temperature (P = 0.002). Cool dialysate (34.4 degrees C) substantially ameliorates hemodialysis-associated hypotension.