Hypoalbuminemia, without any apparent cause, is occasionally seen in elderly patients. Eleven patients (6 with plasma albumin of over 3 gm% and 5 with plasma albumin of 3 gm% or less), who had no evidence of liver disease or nephrosis and whose dietic history suggested that they were taking adequate amounts of protein, were investigated, using 131I human serum albumin. None were acutely ill and their age ranged from 70 to 86 years. It was found that elderly subjects with plasma albumin level of 3 gm% or less had significantly reduced albumin pools and an increased fractional catabolic rate. It is suggested that this may be due to an impairment of the control of degradation in these patients. There was no increased gut loss of albumin in 3 hypoalbuminemic patients investigated with 131I-PVP.