The relationship between topological indices and sorption coefficients ( Koc) based on 543 chemicals was investigated. The range of the experimental Koc values covered 6.4 log-units. Polarity correction factors were introduced. The molecular connectivity indices and polarity correction factors were analyzed by stepwise regression for their contribution to a linear regression model. A model was developed based on data for 400 chemicals and was verified using a testing set including another 143 chemicals. The mean residual was 0.346 log-units for the model and 0.253 log-units for overlapping experimental Koc. The robustness of the model was validated by a modified jackknife test.