1. A new, specific and sensitive urinary assay for separate normetanephrine (NM) and separate metanephrine (M) is described.
2. This test employs high-voltage paper electrophoresis after passage of the urine through a resin column.
3. There is no difference in the urinary excretions of either separate NM or separate M in normotensive or hypertensive subjects.
4. Phaeochromocytoma patients excrete significantly larger amounts of separate NM and separate M than normotensive or hypertensive subjects.
5. Incorrect results are occasionally obtained with other urinary assay tests which measure either the combined metanephrines or different urinary catecholamine metabolites for the diagnosis of phaeochromocytoma.