The molar enthalpies of solution, Delta(sol)H(m)(wc), of a new amino acid ionic liquid 1-butyl-3-methylimidazolium glutamine [Bmim][Glu], containing various amounts of water and with various aqueous molalities, were measured with a solution-reaction isoperibol calorimeter at (298.15 +/- 0.01) K, where wc denotes water content. The standard molar enthalpies of solution of [Bmim][Glu] with given amounts of water, Delta(sol)H(m)(0)(wc) were obtained according to Archer's method. To eliminate the effect of the small amount of water in [Bmim][Glu], a linear fitting of Delta(sol)H(m)(0)(wc) versus the water content was carried out, and the intercept, Delta(sol)H(m)(0) (Pure ionic liquid) = (40.55 +/- 0.06) kJ.mol(-1), is the standard molar enthalpy of solution of anhydrous [Bmim][Glu]. Furthermore, the Glasser's theory of lattice energy was used to estimate the hydration enthalpy of glutamine anion [Glu](-).