Geno3D (http://geno3d-pbil.ibcp.fr) is an automatic web server for protein molecular modelling. Starting with a query protein sequence, the server performs the homology modelling in six successive steps: (i) identify homologous proteins with known 3D structures by using PSI-BLAST, (ii) provide the user all potential templates through a very convenient user interface for target selection, (iii) perform the alignment of both query and subject sequences, (iv) extract geometrical restraints (dihedral angles and distances) for corresponding atoms between the query and the template, (v) perform the 3D construction of the protein by using a distance geometry approach and (vi) finally send the results by e-mail to the user.