To evaluate cardiorespiratory endurance of patients with chronic glomerulonephritis (CGN), ventilatory threshold oxygen uptake (VT) was measured in 69 patients with chronic glomerulonephritis and 337 healthy subjects (male: 140, female: 197) varying in age from 15 to 86 yrs. They underwent ramp exercise test using bicycle ergometer with breath by breath measurement of ventilation and gas exchange variables. VT was determined by visual inspection. In both healthy subjects and patients, VT declined with age and significant negative correlation was found between age and VT in each male and female. VT of the each patient was presented as percentage of the respected value of sex and age-matched healthy subjects (%VT). Mean %VT of all the patients was 88.7 + 21.3% and significantly lower than the healthy subjects. Mean Ccr of the patients was 84.1 + 31.0 ml/min and mean hemoglobin concentration was 13.9 + 1.7 g/dl. Although there was no significant difference in renal function or duration of disease between the patients of sedentary life style and active life style, %VT of the patients of sedentary life style (82.7 + 16.0%) was significantly lower than healthy subjects and the patients of active life style (120.8 + 27.1%). Sedentary life style seems to be the most important factor responsible for the decline of cardiorespiratory endurance in the patients with mild impairment of renal function. Secondary, elongation of duration of disease seems to reduce VT of the patients. %VT of the patients over 1 year (86.6 + 21.9%) is significantly lower than healthy subjects.(ABSTRACT TRUNCATED AT 250 WORDS)