CypRules Server predicts the metabolizing Cytochromes P450 (CYPs) inhibition, including CYP1A2, CYP2C19, CYP2C9, CYP2D6 and CYP3A4. CypRules predicts its results based on C5.0 algorithm. The rules are calculated based on Mold2 2D descriptors. The suggested ruleset that leads to the predicted outcome will be listed as well. This server will be helpful for researcher working in the field of drug discovery. We hope to contribute to decreasing the cost of discovering new drug molecules. Click one of the P450 endpoint listed left and start the prediction!