For the evaluation of vibrational spectroscopic data acquired online to a chem. reaction a broad range of different chemometric algorithms is available. The present study reports the comparative results obtained by different chemometric techniques from the data acquired by light-fiber coupled Fourier-transform near IR (FT-NIR) transmission spectroscopy and Fourier-transform mid-IR (FT-MIR) spectroscopy in the attenuated total reflection (ATR) mode to monitor the soln. polymn. of Me methacrylate (MMA). We have found that the results obtained by the application of multivariate curve resoln. (MCR) methods to the MIR spectral data acquired during the polymn. of MMA are quite comparable to the results derived by partial least-squares calibration. In the case of the NIR data univariate calibration yields somewhat poorer results than multivariate calibration and MCR, but still inside an acceptable range.