This is the homepage of an online journal that disseminates “”articles that significantly advance the study of categorical algebra or methods, or that make significant new contributions to mathematical science using categorical methods.”” A new volume is published each year, consisting of between ten and twenty research papers. The journal commonly focuses on the applications of category theory to computer science, algebra, topology, and other scientific areas. Papers are contributed by researchers and mathematicians from around the world, and they are available for download dating back to 1995.