This volume of the Handbook is the first of a two-volume set of reviews devoted to the rare-earth-based high-temperature oxide superconductors (commonly known as hiTC superconductors). The history of hiTC superconductors is a few months short of being 14 years old when Bednorz and Müller published their results which showed that (La,BA)2CuO4 had a superconducting transition of ~30 K, which was about 7K higher than any other known superconducting material. Within a year the upper temperature limit was raised to nearly 100K with the discovery of an ~90.