The effects of calving on carcass traits particularly depot fat of registered beef cows were investigated in their young stage.The records of ultrasonic carcass estimates were obtained from 300 heads of registered Japanese Black beef cows.These animals were ultrasonically scanned at registration (before calving) and 1 month after calving.Body weight (BW) and body condition score (BCS) were also taken at registration.The data from these cows were analyzed by the least squares procedure to assess the effect of sire, feeding place factor on ultrasonic estimates of carcass traits and the relationships between these traits and their changes pre and post calving.Sire had significant effects on BCS, rib thickness (RT) and intermuscular fat thickness (IMFT) before calving, and subcutaneous fat thickness on the lumbar vertebrae (SFT-LV) changes before and after calving.Feeding place had significant effects on all subcutaneous and intermuscular fat thickness except subcutaneous fat thickness on the 7th rib (SFT-7) before calving and subcutaneous fat thickness on the on the 13th rib (SFT-13) changes before and after calving.The results suggested that feeding place has a great influence on those carcass traits of beef cows.Cows with higher BCS tend to store much amount of subcutaneous and intermuscular fat than the others.In relationships between BCS before calving and changes of carcass traits, there seems to be a difference between the cow groups.BCS before calving will have an effect on the changes of depot fat after calving.