A first web server to perform computer-aided de novo drug design, to build focused combinatorial libraries of molecules and to perform virtual screenings. The de novo drug design tool creates new molecules by using a genetic algorithm to evolve a population of molecules which are gradually improved by competing for the ‘survival of the fittest’. The second tool assists the user in the design of a combinatorial library where a central core is connected to reactants coming, for example, from a supplier. The generated virtual library can be automatically evaluated by using the same scoring function as the one used in the de novo drug design step. It aims to prioritize the reactants.