Genetic studies on closed populations benefit from comprehensive, searchable genealogy resources. To support studies of Anabaptists, a computerized database has been developed that merges two large genealogy books, the "Fisher Family History" and the "Amish and Amish Mennonite Genealogies." The former is more current but the latter is more comprehensive for the 18th and 19th centuries. Therefore, the merger of the two books is significantly more useful than either book alone. We demonstrate the utility of the merged database with two results: an increase in inbreeding coefficients and the identification of parent-child relationships that do not exist in either book. Am. J. Med. Genet. 86:156-161, 1999. Published 1999 Wiley-Liss, Inc.