This index contains the names of over 42,300 Roman Catholic baptisms recorded in Cincinnati and Hamilton County, Ohio between January 1850 and December 1859. The source materials for this work are the microfilm copies of original baptismal registers which were kept by the individual parish churches, and are stored at the Archives of the Archdiocese of Cincinnati. This index contains baptismal records of all twenty-five existing Roman Catholic Churches in Hamilton County, Ohio between January 1850 and December 1859. Due to the size of the publication, it has been divided into two books. Part 1 covers the last names beginning with the letter "A" through "L", and Part 2 covers the last names beginning with the letter "M" through "Z".