Recent improvements in the prediction of protein secondary structure are described, particularly those methods using the information contained into multiple alignments. In this respect, the prediction accuracy has been checked and methods that take into account multiple alignments are 70% correct for a three-state description of secondary structure. This quality is obtained by a 'leave-one out' procedure on a reference database of proteins sharing less than 25% identity. Biological applications such as 'protein domain design' and structural phylogeny are given. The biologist's point of view is also considered and joint predictions are encouraged in order to derive an amino acid based accuracy. All the tools described in this paper are available for biologists on the Web (http/www.ibcp.fr/predict.html).