This book constitutes the refereed proceedings of the 4th International Conference on Formal Concept Analysis, held in February 2006. The 17 revised full papers presented together with four invited papers were carefully reviewed and selected for inclusion in the book. The papers show advances in applied lattice and order theory and in particular scientific advances related to formal concept analysis and its practical applications: data and knowledge processing including data visualization, information retrieval, machine learning, data analysis and knowledge management.