A prospective study on hypotension in hemodialysis was performed in 60 nondiabetic patients at two different dialysate temperatures during 12 months. A 37 degrees C bath (3,723 sessions) was used and after the first 6 months the temperature was changed to 35 degrees C (4,019 sessions). The prevalence of symptomatic hypotension was 15.3% and it was closely correlated with the presence of other symptoms. The most affected populations were women, patients over 55 years of age, patients with low body surface area and patients with a cardiovascular disease. A slight but significant decrease of symptomatic hypotension was seen by using a 35 degrees C dialysate (16.4 vs. 14.3%, p less than 0.01). In patients with frequent hypotension (in up to 30% of sessions), cool dialysate significantly reduced the incidence of the symptom (44.2 vs. 34.1%, p less than 0.001). These results were obtained in spite of a greater interdialysis weight gain at low temperature (2 +/- 0.6 vs. 1.9 +/- 0.7 kg, p less than 0.001). We consider that low-temperature dialysis is a simple, useful and economic procedure, especially for highly symptomatic patients. The association of cooling dialysate with higher sodium concentration, bicarbonate and special membranes could reduce dialysis symptoms dramatically.