Traditionally, China had character dictionaries, but no word dictionaries. Later, small-scale word dictionaries began to appear. Then large-scale word dictionaries began to appear but those only dealt with modern Chinese language. The Hanyu Da Cidian (Unabridged Dictionary of Sinitic) (HDC) is the first large-scale comprehensive word dictionary in Chinese history that includes both ancient and modern language. HDC consists of twelve volumes, almost 20,000 pages, approximately 370,000 entries, 1,500,000 citations, and nearly 23,000 different characters. Well over 100,000 sets in China alone have been sold since its publication. The Hanyu Da Cidian is an excellent, comprehensive dictionary of ancient and modern Chinese, but it is difficult to find items in it because it is arranged by radicals and residual strokes, hence the need for the alphabetical index of words. An Alphabetical Index to the Hanyu Da Cidian provides easy access to all 350,000+ multisyllabic entries found in HDC. It does not include the monosyllabic entries of the dictionary, since a separate alphabetical index has already been published for them. This index uses Hanyu Pinyin (romanization of Modern Standard Mandarin) to provide phonetic annotation for all of the multisyllabic Chinese character entries in the dictionary, enabling the user to locate the entries by means of their alphabetical order. Compilation of this huge index began more than a decade ago, shortly after the first volume of the HDC appeared. The index is characterized by its single-sort alphabetical order which enables users to find an entry in HDC as quickly and effortlessly as locating a word in the ABC Chinese-English dictionaries compiled by John DeFrancis. This gigantic, alphabetically ordered index also serves as a large database that has important implications for research and applications relating to Sinitic Information Technology.