SwissSidechain is a structural and molecular mechanics database and curated platform of hundreds of non-natural amino-acid sidechains that can be used to study in silico their insertion into natural peptides or proteins. Structural files (pdb, mol2, SMILES) for 230 sidechains can be found together with PyMOL and UCSF Chimera plugins to insert them into existing peptide or protein structures. Predicted rotamers as well as topologies and parameters to run molecular mechanics analysis are provided. This tool is provided and maintained by the Molecular modeling group at the Swiss Institute of Bioinformatics. This database is free for academic use.