ANTHEPROT is a fully interactive program devoted to the analysis of protein structures using a graphics workstation. It presents four options: The first option can predict secondary structures using five methods, and hydrophobicity, solvent accessibility, flexibility and antigenicity profiles using eighteen scales. The user may introduce his own scales. The results displayed on the screen can be easily analyzed. The second option is for representing results concerning up to eight proteins by one method. To compare these proteins, it is possible to align the profiles or the predicted secondary structure according to various motifs. The secondary structure deduced from crystallographic data may also be introduced. The third option is designed to compare the primary structure of two proteins and to visualize on the screen regions that exhibit similarity. Six different comparison matrices may be used, but the user can also introduce his own matrices. The last option is for studying the proteolytic peptides resulting from a chemical or enzymatic digestion of a given protein. It is possible to analyze the protein cleavage using eleven chemical reagents or enzymes. The results are displayed on the screen as RP-HPLC chromatogram.