The studies sponsors invited all Judeo-Christian religious bodies listed in the Yearbook of American and Canadian Churches to participate. Final totals include information from 111 Christian and other religious bodies. The 111 groups reported 231,708 congregations with 112,538,310 adherents, which is 49.2% of the total population of 225,011,986. No attempt was made to count strictly independent churches that have no connection with a denomination.

The RCMS collection reports a measure of members and adherents. Members include only those who are designated as full members by the congregation. Congregational "adherents" include all full members, their children, and others who regularly attend services or participate in the congregation. When religious groups reported only adult membership, the following formula was used to derive the number of adherents: The total county population was divided by the total county population less children 13 years and under (derived from census), and the resulting figure was multiplied by the confirmed members. Using adherents allows for more meaningful comparisons between groups that count children as members (e.g., Catholics) and those that don't (e.g. Baptists).

With the assistance of the United Synagogue of America, the full members (individual adult members) of 793 Conservative synagogues were identified by county. With the assistance of the Union of American Hebrew Congregations, the full members of 708 Reform congregations were also identified by county. No county information was available on either full members or adherents of Orthodox synagogues.

Four black denominations, accounting for 1.8 million adherents, participated in the study. Major efforts were made to enlist the participation of the four other large black churches and the 17 smaller black denominations listed in the Yearbook, but without success. Four Orthodox bodies, accounting for combined adherents of 55,000, participated in the study. Although sizeable efforts were made to obtain data for the remaining 17 groups, statistics were not obtained. Besides the denominations mentioned above, there are 11 non-participating church bodies that reported more than 100,000 to the Yearbook of American and Canadian Churches.