This census index, in common with others prepared by Mrs. Bentley, is the standard reference tool on its subject--a work as thorough and as accurate as painstaking labor could make it. Where questions of interpretation occurred, for example, Mrs. Bentley compared her microfilm copy with a photostatic copy of the census, thus obtaining the best possible reading. The index itself consists of an alphabetical list of the heads of households in the 1800 federal census of Massachusetts. First the family name of the head of household is given, followed by the Christian name, then the county of residence, and finally the page number of the census schedule. The 305 pages of text contain data on some 70,000 persons, most of whom were of age during the Revolutionary War, many participating in it. (Researchers should note that the enumerations for Boston and Chelsea in Suffolk County are missing from the extant census returns, an omission which should be anticipated in the index.)