The purpose of the study was to assess the influence of chronic kidney and liver diseases on the transcortin concentrations in plasma. The mean (+/- SD) plasma concentration of transcortin was 45.0 +/- 6.7 mg/l in women not taking oral contraceptive steroids and 41.2 +/- 6.7 mg/l in healthy male volunteers. Patients with the nephrotic syndrome had low transcortin concentrations (females: 20.9 +/- 8.5 mg/l; males: 26.0 +/- 6.0 mg/l). Abnormally low concentrations were measured in females treated for endstage renal disease with chronic ambulant peritoneal dialysis (CAPD) (30.8 +/- 7.5 mg/l). Patients on hemodialysis or with a functioning renal allograft had normal transcortin concentrations in plasma. Females suffering from a primary biliary cirrhosis had normal transcortin concentrations and male patients with an alcoholic cirrhosis had abnormally low mean transcortin concentrations in plasma (32.6 +/- 7.4 mg/l). The transcortin concentrations in patients with a Gilbert syndrome were normal. Among patients with a kidney or liver disease, the large variability of the transcortin concentration in plasma indicates that the knowledge of the transcortin concentration or the unbound steroid concentration in plasma is mandatory for the interpretation of total glucocorticoid concentrations in plasma.