['We investigated the influence of gender on the diurnal regulation of urine production with special focus on vasopressin, oxytocin and prostaglandin E2.', 'Fifteen young women in mid-follicular phase and 22 young men (20-33\xa0years) were included. All participants underwent a 24-h circadian inpatient study under standardized conditions for measurements of plasma vasopressin, oxytocin, sodium and osmolality. Urine was fractionally collected for measurements of electrolytes, aquaporin-2 and prostaglandin E2.', 'Plasma vasopressin expressed a diurnal rhythm with a night-time increase in both genders (P\xa0<\xa00.001). The ratio between mean daytime and mean night-time was 1.57 [95% CI: 1.33-1.84] P\xa0<\xa00.001 in men and 1.35 [95% CI: 1.11-1.64] P\xa0=\xa00.002 in women. P-vasopressin was higher in males during the night (P\xa0<\xa00.05). There was no difference in diuresis (P\xa0=\xa00.43), urine osmolality (P\xa0=\xa00.12) or aquaporin-2 excretion (P\xa0=\xa00.80) between genders. We found a trend towards a higher reabsorption of free water in males (P\xa0=\xa00.07). The excretion of prostaglandin E2 was higher in males (P\xa0<\xa00.001). There was no diurnal rhythm in p-oxytocin (P\xa0=\xa00.37) and no correlation to diuresis, urine osmolality or aquaporin-2 excretions.'] Does urinary concentration exclusively rely on plasma vasopressin . A study between genders . Gender and diurnal urine regulation?