A new molecular representation, molecular hologram, is employed to investigate the quantitative relationships between gas chromatographic retention indices (GC-RI) and molecular structures of polychlorinated dibenzofurans (PCDFs). Together with application of partial least squares (PLS) regression, the quantitative structure-reten- tion relationship (QSRR) model is constructed for GC-RI of 135 PCDFs. This new QSRR model presents high statistical quality and predictive value with crossvalidation correlation coefficient q2LOO values of 0.998, and non-crossvalidation correlation coefficient r2 of 0.998. 100 PCDFs are selected randomly as training set and the rest as testing set. The result of PLS regressive analysis of training set yields r2 of 0.998 and q2LOO of 0.997. The GC-RIs of testing set are predicted, and the correlation equation indicates that the model based on training set has excellent ability to predict the GC-RIs of PCDFs in testing set.