1. Urinary excretion of prostaglandins E2 and F2α were determined in 11 women with phaeochromocytoma and in 23 healthy women.
2. In patients with phaeochromocytoma a significant decrease in urinary excretion of PGE2 and a significant increase in urinary excretion of PGF2α were observed in comparison with controls.
3. Decreased urinary PGE2 and increased urinary PGF2α excretion suggest impaired renal prostaglandin synthesis or metabolism.
4. High PGF2α excretion in association with reduced PGE2 excretion may reflect enhanced activity of 9-ketoreductase, probably caused by excess catecholamines.