Abstract: The present invention relates to the design of libraries, such as combinatorial libraries, which may be used in the discovery of novel potentially useful compounds. The invention operates on a population of libraries that is refined iteratively. The refinement involves the following steps: calculating the relative dominance of the libraries in the population; selecting libraries for modification according to dominance; modifying the selected libraries using genetic operators; and inserting the modified libraries back in the population. The refinement steps are repeated until adequate convergence is deemed to have occurred or for a specified number of iterations. The Pareto optimal set of libraries in the final population is output for further processing such as storage or manufacture.