The resonances originating from high-molecular weight macromolecules (MM) underlie those of metabolites in brain 1H NMR spectra. In humans, MM content and MM pattern have been shown to depend on age of the subject. In this project, the influence of age-specific MM pattern on MR quantification was investigated. The age-associated differences in the MM pattern have a major influence on the quantification of metabolite concentrations in the aging brain which might lead to different interpretation of the data. This important finding suggests that the age-specific MM spectrum should be used in the basis set to obtain accurate concentrations of metabolites.