The urinary concentrations of hydroxyproline (HYPRO)and 3－methyl histidine (3－MEH1S ) were derntermined in 16 Chinese－Holstein cows. The objectives of the experiment were to find out thhe relationship rnbetween collagen and myosin ddegradation and uterine involution in the postpartum cow. The results in the rnexperiment showed that the mean concentrations of HYPRO and 3－MEHIS were 138.92±22.99 and 37.09rn± 3.90 nmol · mL-1 ,respectively ,for the cows during the days between 60～90 postpartum ,and for the covs rnimmediately after calving the concentrations of HYPRO and 3－MEHIS reduced from 284.30 and 65.I8 nmol rn · mL-1 on the day one after calving to the normal level of 109.18 and 33.51 nmol · mL－1 on the day 50 postrnpartum ,respectively. There was a good correlation between the urinary concentrations of both HYPRO and 3rn－MEHIS and the diameters of the involuting uterus ( r ＝0.79).