A total of 87 sows (Line 241, DNA) and their offspring were used to evaluate the effect of increasing standardized ileal digestible (SID) lysine through increasing soybean meal (SBM) concentration in late gestation diets on lactating sow and litter performance. Sows were blocked by parity and body weight (BW) on approximately d 90 of gestation and allotted to 1 of 3 treatments with 29 replications per treatment. Diets included increasing SID lysine (0.60, 0.80, or 1.00%) through increased SBM (14, 21, or 29% of the diet). Sows received approximately 2.04 kg/d of their treatment diet for an average SID Lys intake of 11.9, 15.8, or 19.9 g/d, respectively. Diets were fed from d 90 of gestation until farrowing. After farrowing, all females were fed a common lactation diet containing 1.10% SID Lys until weaning (19 d post-farrow). Sow BW, caliper score, and backfat and loin depth were collected on d 90, upon entry into the farrowing house (d 110), and at weaning. Urine samples were collected on d 90 and 110 of gestation to ascertain urinary creatinine levels. Litters were cross-fostered within sow treatment by 48 h after farrowing to equalize litter size. Parity was included in the statistical model as a fixed effect with females being classified as either a primiparous (n=35) or multiparous (n=52) sow. Weight gain from d 90 to 110 of gestation increased as SID Lys increased (linear, P < 0.001). There were no differences in starting litter size or piglet birth weight with increasing SID Lys in late gestation (linear, P > 0.10). Change in urinary creatinine level from d 90 to 110 of gestation tended to decrease as SID Lys increased in the diet (linear, P = 0.063) suggesting that less muscle catabolism occurred with increasing SID Lys. Piglet ADG from d 2 to 10 of lactation linearly increased as SID Lys increased (P = 0.017), but not from d 2 to weaning. From d 2 until weaning, litters from sows fed the 0.80% SID Lys gestation diet had the highest litter gain (quadratic, P = 0.044). Pre-weaning mortality from birth until d 2 of lactation was highest for sows fed 0.80% SID Lys (quadratic, P = 0.025). There was a parity × gestation diet interaction for pre-weaning mortality from d 2 to weaning (P = 0.049) where mortality increased as SID Lys increased in primiparous sows but decreased in multiparous sows.