The potential of near-infrared (NIR) spectroscopy for the determination of secondary metabolites in leaves of differentMenthaspecies was investigated. Based on the reference values, received by hydrodistillation and gas chromatography, respectively, the correlation strength between these data and the NIRS prediction is shown by the R2statistics. Furthermore, the standard error of cross validation (SECV) was found to be the best additional estimate of prediction accuracy. In contrast to the time consuming reference methods, NIRS allows the analyst to predict the content of most importantMenthaterpenoids already after an analysis time of approximately one minute simultaneously. The study demonstrates that NIRS can be successfully applied as a rapid method not only in breeding research and during growth in the fields, but also to determine the individual oil quality after distillation, blending and rectification processes.