A nonmonotonous dependence of luminescence intensity of aqueous solutions of 0.1 M glycine and its N-methyl derivatives on the number of methyl groups in the solute molecule was found. A correlation between luminescence intensities and optical density at the excitation wavelength of 300 nm was revealed. Possible causes of the phenomenon observed were analyzed. Among these are: luminescence of admixtures, intrinsic luminescence of dissolved molecules, and luminescence related to the formation of nanoscale complexes in solution. On the basis of the data, it is impossible to make a final choice between the three above-mentioned mechanisms of luminescence of aqueous solutions of glycine and its N-methyl derivatives.