The multidrug transporter P-gp (P-glycoprotein) attracts a lot of attention because it affects drug absorption, distribution, metabolism and excretion etc. It is important in both cancer research and drug discovery. The sdf structure file is downloaded from Wang et al . The authors used super vector machine (SVM) for modeling to predict whether a compound is substrate or non-substrate, and the best model gave a prediction accuracy of 0.88 on the test set. The accuracy in Wang's paper is error-rate which can be computed by the ratio of the number of the successful cases over the total number of the cases in the test data set.