The defined secondary structure of proteins method is often considered the gold standard for assignment of secondary structure from three-dimensional coordinates. However, there are alternative methods. 2Struc: The Secondary Structure Server has been created as a single point of access for eight different secondary structure assignment methods. It has been designed to enable comparisons between methods for analyzing the secondary structure content for a single protein. It also includes a second functionality, Compare-the-Protein to enable comparisons of the secondary structure features from any one method to be made within a collection of nuclear magnetic resonance models, or between the crystal structures of two different proteins.