Nonspecific symptoms are common in dialysis patients but few methods are available to measure their severity and their response to alteration in dialysis therapy. To determine the clinical features and measure the severity of the most important symptoms in end-stage renal disease (ESRD) patients, 97 dialysis patients were interviewed, 63 of whom were reinterviewed 1 year later. For comparison 82 transplant recipients were also interviewed. The six most important symptoms in dialysis patients (using the product of the patient's perception of severity and prevalence) were tiredness, cramps, pruritus, dyspnea, headaches and joint pain. The symptoms were long-standing, occurred frequently, with little difference in prevalence between hemo- and peritoneal dialysis patients, and were often unrelated to a hemodialysis session. For each symptom, several dimensions of severity were assessed including frequency, duration, effect on sleep, daily living, activity, subjective quality of life and necessity for drug therapy. Often these dimensions did not correlate with patient's perception of severity. For each symptom these items were combined to give an aggregate score with a range 0-10. Interobserver reproducibility for each symptom score was greater than or equal to 0.7 but intraobserver reproducibility was poor for 3 symptoms, because of the fluctuating nature of the symptoms. Construct validity was demonstrated by finding a significantly worse distribution of aggregate scores for tiredness, cramps, pruritus, dyspnea and nausea/vomiting in dialysis compared to transplant patients. Aggregate scores changed little after 1 year's follow-up in stable dialysis patients but significant improvement in the aggregate scores for tiredness, dyspnea and nausea/vomiting were observed in 14 patients after successful transplantation.(ABSTRACT TRUNCATED AT 250 WORDS)