Multiparous Holstein cows (n = 57) averaging 124 DIM at the start of the experiment were used to determine production responses to supplementation with rumen-protected Lys and 2 forms of rumen-protected Met. Following a 2-wk covariate period, cows were assigned to one of 3 treatments in a completely randomized design. Treatments were formulated using the Cornell Net Carbohydrate and Protein System (version 6.5.5) and consisted of control [C; Met at 2.30% of metabolizable protein (MP) supply and 0.98 g MP-Met/Mcal of metabolizable energy (ME); Lys at 6.68% of MP and 2.85 g MP-Lys/Mcal of ME]; AA-S [Met at 2.66% of MP and 1.14 g MP-Met/Mcal of ME; Lys at 7.16% of MP and 3.08 g MP-Lys/Mcal of ME]; and AA-M [Met at 2.66% of MP and 1.14 g MP-Met/Mcal of ME; Lys at 7.16% of MP and 3.07 g MP-Lys/Mcal of ME]. Lysine was supplemented to AA-S and AA-M using USA Lysine (Kemin Industries, Des Moines, IA). Methionine was supplemented to AA-S using Smartamine-M (Adisseo, Alpharetta, GA) and to AA-M using MetiPEARL (Kemin Industries, Des Moines, IA). Data were analyzed using the MIXED procedure of SAS (SAS Institute, Inc. Cary, NC) with repeated measures. Contrasts consisted of AA (control vs. both AA treatments) and Met (AA-S vs. AA-M). Dry matter intake (26.0, 25.8, and 25.5 kg/d for C, AA-S, and AA-M, respectively; P = 0.54) and milk yield (45.0, 44.5, and 44.9 kg/d; P = 0.84) were not different among treatments. Milk true protein percentage (2.92, 2.99, and 2.98%) was increased (P = 0.01) for cows fed AA-S and AA-M compared with controls, but was not different between AA-S and AA-M (P = 0.81). Yield of milk protein (1.32, 1.32, and 1.35 kg/d; P = 0.58) was not different among treatments. Percentages (3.46, 3.56, and 3.51%; P = 0.54) and yields (1.56, 1.57, and 1.59 kg/d; P = 0.82) of milk fat and yields of energy-corrected milk yield (45.3, 45.0, and 45.7 kg/d; P = 0.75) were not different among treatments. Supplementation of AA increased milk true protein percentage but did not affect yields of milk and milk components; responses were the same between the 2 forms of rumen-protected Met used in this experiment.