The objective of this study was to investigate the relationship between behavioral signs and duration of estrous in Hanwoo and Holstein cattle for the prediction of optical insemination. Fifty two of 58 and 71 of 89 in Hanwoo and Holstein cows or heifers showed estrous exhibition within 72 h after 2 days following $PGF_{2}alpha$ administration, respectively. The number of mounting and standing heat were 54.2 and 57.6, 59.4 and 53.5, 42.0 and 30.8 and 16.2 and 10.7 times in Hanwoo cows, Hanwoo heifers, Holstein cows and Holstein heifers, respectively. Duration of mounting were no significantly difference for Hanwoo cows ($21.2pm11.3$), Hanwoo heifers ($19.9pm11.4$), Holstein cows ($8.7pm4.4$) and Holstein heifers ($16.9pm8.0$). Duration of standing heat were significantly (p<0.05) shorter for Holstein cows ($5.4pm3.4$) than for Hanwoo cows ($17.1pm9.6$), Hanwoo heifers ($16.5pm6.3$) and Holstein heifers ($15.0pm7.2$). Time until mounting after injection of $PGF_{2}alpha$ were significantly (p<0.05) longer for Holstein cows ($56.3pm11.45$) than for Hanwoo cows ($42.71pm10.44$), Hanwoo heifers ($36.6pm8.21$) and Holstein heifers ($40.70pm6.15$). Time until standing heat after injection of $PGF_{2}alpha$ were significantly (p<0.05) longer for Holstein cows ($61.6pm8.92$) than for Hanwoo cows ($46.2pm11.49$), Hanwoo heifers ($42.7pm6.06$) and Holstein heifers ($44.1pm6.72$). In the results of this study, duration of standing heat was the shortest in Holstein cows ($5.4pm3.4$). The estimation of estrous with Holstein cows has more difficulty because to significantly shorter duration of standing heat than for Hanwoo cows, Hanwoo heifers and Holstein heifers. The standing heat can be a good predictor for time of ovulation but it is concluded that mounting behavior could be the best predictor for time of ovulation.