1. Two techniques for estimating plasma aldosterone concentration are compared by means of repeated assays of a plasma pool and also by analysis of a wide range of plasma samples.
2. No significant difference was found in the results obtained by the methods. Radioimmunoassay required only one tenth of the volume of plasma needed for the double-isotope derivative method.
3. Its rapidity and relative inexpensiveness makes radioimmunoassay at present the most suitable technique for large-scale population screening.