1. Measurement of urinary 6-ketoprostaglandin (PG) F1α and PGE2 excretion in 83 healthy children, aged 5-15 years, revealed that supervised 4 h urine collections under mild water diuresis provided more consistent results than overnight 12 h urine collections.
2. Males had higher urinary excretion of 6-keto-PGF1α but not of PGE2 compared with females.
3. Urinary potassium was related to 6-keto-PGF1α in both 4 and 12 h urine collections and urinary sodium to 6-keto-PGFα in 4 h collections only.
4. In the sexes combined multiple regression analyses revealed age as the only significant influence on prostanoid excretion (P = 0.001).
5. Thus age and sex and dietary potassium intake need to be considered in studies of urinary prostanoids in children.