A comprehensive quantitative characterization of Maillard reaction products was carried out for conventional (CON) and lactose-hydrolyzed (LH) ultrahigh temperature (UHT) milk during storage at 20, 30, and 40 °C for 1 year. The accumulation of 3-deoxyglucosone (3-DG) and 3-deoxygalactosone (3-DGal) in LH-UHT milk ranged from 20-fold (at 20 °C) to 44-fold (at 40 °C) higher than that in CON-UHT milk. High temperature storage (40 °C) significantly accelerated the accumulation of 3-DG, 3-DGal, and 5-hydroxymethyl furfural but not the majority of the analyzed advanced glycation endproducts (AGEs). The concentrations of major AGEs including N-ϵ-carboxymethyllysine (CML), N-ϵ-carboxyethyllysine (CEL), methylglyoxal-hydroimidazolone isomers (MG-H1/H3), glyoxal-hydroimidazolone isomers (G-H1/H3), and G-H2 detected in CON milk during storage were in the range 12-700, 1-14, 8-45, 4-13, and 1-30 μM, respectively, while they were 30-570, 2-88, 17-150, 9-20, and 5-34 μM, respectively, in LH milk. Pyrraline, S-(carboxymethyl)cysteine (CMC), and glyoxal-lysine dimer were detected in lower levels, while MG-H2, methylglyoxal-lysine dimer, argpyrimidine, glyoxal-lysine-amide, glycolic acid-lysine-amide, and pentosidine were not detected in any of the milk samples. This work demonstrates for the first time that five of the analyzed AGEs (CML, CEL, MG-H1/H3, G-H1/H3, and G-H2) could be selected as markers for evaluation of the extent of the Maillard reaction in UHT milk. These results contribute to a better understanding of how Maillard reactions progress during storage of UHT milk and can be used to develop strategies to inhibit Maillard reactions in LH milk.