The FTIR quantitative evaluation of grafting succinic anhydride onto polypropylenes is presented. It was done by correlating relative absorbance values obtained from IR spectra with grafting levels of the sample as determined by an improved traditional hot titration method. The results obtained seem to be valid for either atactic or isotactic modified polypropylenes and suggest a careful review about how this technique is usually used in the quantification of polar groups grafted onto polyolefins.