We examined clinical and laboratory features retrospectively in 402 patients at the start of chronic hemodialysis in order to define better the "uremic syndrome" in the dialysis era. The information gathered included demographic data, renal diagnoses, uremic symptoms, biochemical values, and prevalences of hypertension (69%), diabetes mellitus (23%) and ischemic heart disease (16%). Unexpected findings were the wide ranges of serum creatinine levels (3.5 to 35 mg/dl) and blood urea nitrogen levels (35 to 345 mg/dl), and the frequency of hyponatremia (27%), hypoalbuminemia (52%), and anion gaps above 25 mg/dl (5%). There were higher hematocrits in males and diabetics, lower serum creatinine levels in females, diabetics and older patients, and lower blood urea nitrogen levels in blacks. The time interval from diagnosis of diabetes mellitus to initiation of dialysis in patients with diabetic nephropathy due to juvenile-onset diabetes mellitus (20.6 +/- 6.8 years) was twice that in adult onset diabetes mellitus (10.3 +/- 8.3 years).