Many fundamental processes involve protein-protein interactions. Recent advances in technology make it possible to perform large-scale, genome-wide interaction mapping experiments that result in an always increasing amount of data. Protein-protein interaction databases are thus becoming a major resource for investigating biological networks and pathways. In this chapter we describe the Molecular INTeraction database (MINT). The MINT database aims at storing, in a structured format, information about protein-protein interactions (PPIs) by extracting experimental details from work published in peer-reviewed journals.