The pharmacokinetics of furosemide 40 mg i.v. were compared in 7 anephric patients and in 7 normal subjects. The average serum clearance was 66 ml/min in the patients and 219 ml/min in the normal subjects, and the corresponding weight corrected clearances were 1.33 ml/min . kg and 2.96 ml/min . kg. Binding to serum proteins was significantly decreased in the anephric subjects, in whom a significant negative correlation was found between the percentage binding and the volume of distribution VDSS. In the patients, but not in the normal subjects, there was a significant positive correlation between VDSS and serum clearance. Both in normal and anephric individuals 4-chlor-5-sulphamoyl-anthranilic-acid (CSA) was found, but there was no evidence of special accumulation either of CSA or anthranilic acid in the anephric patients. In the patients the initial increase in serum concentration of sodium and protein followed by a more conspicuous decrease were more pronounced, but none of the changes were statistically significant.