This study proposes an experimental method to quantify the molecular orientation of the crystalline phase of isotactic polypropylene from polarized Raman spectroscopy measurements. The method is based on the intensity sensitivity of two Raman scattering bands located at 973 (C-C stretching mode) and 998 cm(-1) (CH(3) rocking mode) to laser light polarization. The first part of this article is devoted to the validation of the method by comparing Raman and Wide Angle X-ray Scattering (WAXS) results obtained on postmortem test samples uniaxially deformed at growing levels. Second, the method is applied to follow the molecular orientation in situ during a tensile test by combining a video-controlled test machine and a Raman spectrometer. Postmortem results show a quantitative agreement between Raman and WAXS measurements. In situ results mainly evidence the ability of the Raman method to characterize molecular orientation in real-time with less than 5 s time resolution. POLYM. ENG. SCI., 51: 1607-1616, 2011. (C) 2011 Society of Plastics Engineers