At its inception in 1972, the end-stage renal disease (ESRD) program was conceived with a set of assumptions about cost, rate of growth, and treatment outcomes in its client population. Despite the potential to correct anemia with recombinant erythropoietin (EPO) introduced in 1987 and improved survival, the level of physical activity among some segments of the hemodialysis population remains suboptimal. This study was undertaken, among other reasons, to identify correlates of poor functional status as measured by a modified Karnofsky scale. Using a modified Karnofsky scale, we measured the functional status of 430 patients who had been treated by hemodialysis for at least 1 year and some of whom were also receiving concomitant treatment with EPO. Patients studied were randomly selected from eight dialysis units in urban New York and suburban New Jersey. A Karnofsky score of less than 70 indicated frank disability--the subject was unable to perform routine living chores without assistance. In addition, current vocational activity was ascertained, and comorbid conditions were quantified. The necessity for wheelchair dependence was noted for each patient. The mean age (+/- SD) of the study population was 56 +/- 14 years (range, 21 to 92 years). Subjects had been on maintenance hemodialysis for 4.09 +/- 3.8 years (range, 1 to 23 years). The study group included 215 men and 215 women, of whom 65% were black, 27% white, 6% Hispanic, and 2% Asian; 36.5% had diabetes mellitus. Although 376 members (87%) of the study group were under treatment with EPO, the mean hematocrit of the study population was only 29% +/- 4.5%.(ABSTRACT TRUNCATED AT 250 WORDS)