The cytochrome P450 (CYP) enzymes play the central role in synthesis of endogenous substances and metabolism of xenobiotics. The substitution of single amino acid caused by non-synonymous single nucleotide polymorphism (nsSNP) will lead to the change in enzymatic activity of CYP isozymes, especially the drugmetabolizing ability. CYP-nsSNP is a specialized database focused on the effect of nsSNPs on enzymatic activity of CYPs. Its unique feature lies in providing the qualitative and quantitative description of the CYP variants in terms of enzymatic activity. In addition, the database also offers the general information about nsSNP and compounds that are involved in corresponding enzymatic reaction. The current CYP-nsSNP can be accessible at http://cypdatabase.sjtu.edu.cn/ and includes more than 300 genetic variants of 12 CYP isozymes together with about 100 compounds. In order to keep the accuracy of information within database, all experimental data were collected from the scientific literatures, and the users who conducted research to identify the novel CYP variants are encouraged to contribute their data. Therefore, CYP-nsSNP can be considered as a valuable source for experimental and computational studies of impact of genetic polymorphism on the function of CYPs.