The charts of 70 successive patients presenting for dialysis therapy for end-stage renal disease (ESRD) were evaluated for their serum electrolyte values. The "classical" pattern of low total CO2 (tCO2), elevated anion gap ("delta"), and normal chloride was found in a minority of patients (14 of 70, or 20%). Hyperchloremia was noted in 46%; in 21 patients (30%), this was associated with a normal delta and in 11 (16%), hyperchloremia was accompanied by an elevated delta. Fourteen patients (20%), most with diabetic nephropathy, had normal serum electrolytes. Patients with chronic glomerulonephritis had a hyperchloremic pattern as often as not, and two of four patients with interstitial nephritis demonstrated hyperchloremia without an elevated delta. We conclude that the previously held thesis that hyperchloremia is a rare or absent finding by the time renal failure progresses to ESRD is no longer tenable. Furthermore, a significant minority of ESRD patients may require the initiation of dialysis at a time when their serum electrolytes are still normal.