Renal urea conservation was evaluated in Corriedale ewes during late pregnancy and lactation. Glomerular filtration, renal plasma flow and urea clearance were significantly reduced both states compared with control sheep. Filtered load of urea and urine urea elimination were significantly reduced during lactation (−46% and −45%, respectively, vs. controls). No changes were noted in fractional excretion of urea. Therefore, Corriedale ewes restrict urine urea losses during lactation by reducing glomerular filtration. During late pregnancy, urea sparing is less marked. Key words: Renal functions, urea, pregnancy, lactation, sheep