The present work reports the concentrations of aluminum in whole blood and dialysis solutions of 27 patients with chronic renal failure and under hemodialysis treatment at Miguel Pérez Carreño and University Hospitals, both from Caracas city. Aluminum levels of the water used to prepare the dialysates were also monitored and the metal mobilization during dialysis studied. Patients' mean blood aluminum concentrations (ca. 34 micrograms AI/L) were lower than those of renal individuals from Maracaibo (ca. 58 micrograms AI/L), situation related to the low metal contents of the dialysate water (ca. 14 micrograms AI/L). In addition, Caracas drinking water showed up very high aluminum concentrations, above 475 micrograms/L. There was a relationship between the renal patients' blood aluminum concentrations and (1) the metal contents of the dialysis solutions and (2) the ingestion of aluminum hydroxide-based antacids. Aluminum transfer incorporation processes toward the patients' blood were observed in both dialysis units. This was due to the favorable concentration gradients (blood aluminum concentration/dialysate aluminum concentration) established at the start of every hemodialysis treatment.