Abstract: We here present the web-based tool TEST for searching T-cell epitopes based on the experimental data from positional scanning synthesized combinatorial libraries (PS-SCL). Implemented with a strong statistical analysis package, relational database and Java applets, the TEST tool first generates scoring matrix, then uses the matrix to scan and score all possible peptides in the user specified protein database. Lab information management functions such as data storage, data retrieval, and data comparison are also provided. The TEST tool has been applied to a variety of T cell clones having known or unknown specificities with reliable predictions. The system should prove useful for the identification of target antigens in infectious diseases, autoimmune disorders, and tumors, and also for the development of vaccines.