Since no effect on CP and diet type on the optimal Trp-to-Lys ratio (TLR) was found in two previous experiments, two extra experiments were planned. In the first one, piglets were fed a Lys-deficient basal diet supplemented with crystalline Lys (to create graded levels of SID Lys). GFR and PUN were measured every 5-d for 15-d; and were analyzed using the broken-line analysis to determine the Lys requirement. As SID Lys level increased, GFR increased linearly and PUN decreased linearly. The SID Lys requirement for was estimated to be 1.02%. To determine the optimal TLR, pigs were fed Trp-deficient basal diet supplemented with crystalline Trp (to create graded levels of SID TLR). Most of the parameters evaluated failed (P > 0.10) to yield an estimate. Based on the evidence we suggest that the optimal SID TLR for early-weaned pigs fed a wheat-barley diet lies below 17.75%.