Three experiments (Exp. A, B and C) were conducted to determine the lysine requirements of PIC (327 x C22) barrows over the growing-finishing period, using plasma urea nitrogen (PUN) as a rapid response criterion. In Exp. A, either randomized complete block designs or completely randomized designs were used. Pretreatment PUN was used as a covariate. Results indicated that the true ileal digestible lysine requirements were 16.5 +/- 0.2, 18.0 +/- 0.5, 20.2 +/- 1.5, 16.7 +/- 0.8, and 14.4 +/- 7.2 g/d/pig at 33, 52, 72, 93, and 113 kg body weight, respectively. The precision of the estimation decreased when pigs reached the finishing period. To increase the precision, three trials in Exp. C were conducted. Repeated 5 x 5 Latin square designs were used and feed intakes were limited to 90% of the ad libitum levels. The estimated true ileal digestible lysine requirements were 19.9 +/- 0.57, 17.0 +/- 0.47, and 18.1 +/- 0.64 g/d/pig at the body weight ranges of 59 to 78, 78 to 95, and 96 to 115 kg, respectively. The last requirement might be overestimated because of a rapid feed consumption during the trial period. Compared with Exp. A, the precision of the lysine requirement estimation increased in Exp. C.;From the lysine requirements obtained in Exp. A and C, the lean growth rates of individually penned PIC barrows were calculated to be 334, 372, 404, 414, 340, 327, and 276 g/d at 33, 52, 69, 72, 87, 93, and 113 kg body weight, respectively. Fitting the data to a polynomial least square regression, a lean growth curve was derived: Y = (-0.11606 + 0.04895X - 0.0005855X2 + 0.000001963X3) x 347, where Y was the lean growth rate in grams/day, X was the BW in kilograms.;Exp. B determined the lysine requirements of PIC barrows under group penned situation. The results showed that each barrow required 15.8 +/- 1.7 and 18.9 +/- 1.4 g true ileal digestible lysine/d at 32 and 50 kg body weight, respectively. PUN responses did not allow valid estimates of the lysine requirements for group penned finishing pigs.