This study was undertaken with three objectives : to determine the optimal time of blood collection for plasma urea nitrogen(PUN) analysis, to examine the frequency distribution of PUN levels in recipient herd and to relate concentration of PUN to conception rate in Hanwoo recipients. The relationship between PUN level and time postfeeding was examined for 5 individual cows. Mean concentration of PUN rose for 4hrs postfeeding and decreased to PUN level before feeding at 10hrs postfeeding. And then, the blood for PUN analysis was collected at the time before feeding in next experiments. The ratio of cows with PUN concentration of < 12, 12∼18 and 18mg/dl were 50.6, 39.9 and 9.5% in 163 recipients, individually. The pregnancy rate of cows with PUN concentration 12∼16 mg/dl (63.3%) was higher than that of cows with PUN concnetration < 12 mg/dl (46.7%) or > 16mg/dl (42.9%). There results suggest that the PUN test may be beneficial for management of recipient herd in effects to maintain or improve reproductive efficiency.