A total of 131 sows (Line 241; DNA, Columbus, NE) were used in a study to evaluate the effect of increasing soybean meal concentration in lactating sow diets on sow and litter performance. Sows were blocked by body weight (BW) and parity on d 112 of gestation, and allotted to 1 of 3 treatments of increasing soybean meal (25%, 30%, or 35% of total diet). Diets were formulated to 1.05% standardized ileal digestible (SID) lysine with L-lysine HCl decreasing as soybean meal increased. All other amino acids and nutrients were formulated to meet nutrient requirement recommendations.2 Diets were fed from d 112 of gestation until weaning (d 20 ± 2). Litters were cross-fostered up to 48 h after farrowing to equalize litter size. Increasing soybean meal concentration increased (linear, P = 0.017) sow BW loss and tended to increase (quadratic, P = 0.052) sow backfat loss from farrowing to weaning. Sow average daily feed intake from d 0 to 7 was similar (P > 0.10) across dietary treatments. However, from d 7 to 14, d 14 to weaning, and overall, average daily feed intake decreased (linear, P = 0.01) as soybean meal concentration increased. There was no evidence for difference (P > 0.10) in wean to estrus interval, litter size, litter weight, or litter weight gain between dietary treatments. Sow serum urea nitrogen concentrations taken on d 14 of lactation increased (linear, P = 0.001) as soybean meal concentration increased. However, there was no difference (P > 0.05) for sow creatinine concentration, regardless of dietary treatment, suggesting the increased urea nitrogen was a reflection of the increased dietary crude protein (CP) as opposed to increased protein catabolism.