Urinary excretion of prostaglandins E2, F2 alpha, E-M (7 alpha-hydroxy-5, 11-diketotetranor-prosta-1, 16-dioic acid), 6-keto F1 alpha, 2,3-dinor-6-keto-F1 alpha, thromboxane B2, 2,3-dinor-thromboxane B2 and 11-dehydrothromboxane B2 was determined by gas chromatography-mass spectrometry in 83 healthy subjects aged one day to 37 years. The excretion rates of all prostanoids increased with advancing age. After correction for 1.73 m2 body surface area, only urinary excretion rates of prostaglandins E-M and 6-keto-prostaglandin F1 alpha depended on age. Reference intervals were calculated as the 10th and 90th percentiles for prostaglandins E2 (4-27 ng/h/1.73 m2), F2 alpha (23-87 ng/h/1.73 m2), 2,3-dinor-6-keto-F1 alpha (4-19 ng/h/1.73 m2), thromboxane B2 (1-21 ng/h/1.73 m2), 2,3-dinor-thromboxane B2 (8-36 ng/h/1.73 m2) and 11-dehydro-thromboxane B2 (15-87 ng/h/1.73 m2) in all subjects, and for prostaglandins E-M and 6-keto-prostaglandin F1 alpha in subjects aged 30 days or less (110-1140 ng/h/1.73 m2 and 7-23 ng/h/1.73 m2) and older than 30 days (62-482 ng/h/1.73 m2 and 2-12 ng/h/1.73 m2). High urinary excretion of prostaglandins E-M and 6-keto-F1 alpha during the newborn period and some distinct changes in urinary excretion of prostaglandin E2 and thromboxane B2 with advancing age suggest that these prostanoids might play a specific role during child development.