The Holter Research Foundation, Inc. Records are arranged in seven subgroups: Holter Research Foundation, Inc. Subgroup; Norman J. Holter Subgroup; Norman J. Holter/U.S. Navy Subgroup; Norman J. Holter/University of California San Diego Subgroup; and Society of Nuclear Medicine Subgroup; Montronics, Inc.; and the Mountain States Telephone and Telegraph Company.

The Holter Research Foundation, Inc. Subgroup consists of the following materials: general correspondence (1947-1985) which includes correspondence logs (1947-1953) and correspondence arranged primarily chronologically with a few titled folders (e.g. "HRF-Hinkle, 1962-1982") filed at the end of the chronological run; interoffice correspondence (1947-1983) between Holter and members of the foundation's staff and Board of Trustees arranged chronologically; miscellaneous correspondence (1953-1978); financial records (1947-1985) including expenditures, grant accounts, invoices, insurance, ledgers, donations, pension plan, taxes, trust accounts, etc.; laboratory records (1948-1982) including laboratory notebooks kept by staff members, calendars, data sheets, diagrams, monitor records, seismic records, radioisotope records, etc.; legal documents (1948-1981); minutes (1950-1983) for the Board of Trustees and members; organizational material (1947-1984); photographs (1948-1971) of staff members, experiments, equipment, etc.; press releases (1947-1973); printed material (1948-1984) arranged as those citing the work of Holter Research Foundation (arranged alphabetically by author), as those reflecting the commercial production of Holter monitoring equipment (arranged alphabetically by company name), and miscellaneous printed material (arranged alphabetically by subject); reports (1950-1983); subject files (1949-1982) arranged alphabetically by title (most titles given by Holter); miscellany (1948-1982); and clippings (1946-1983).

The Norman J. Holter Subgroup contains biographical material (1941-1978); general correspondence (1914-1983) arranged chronologically and dealing with family matters, personal investments, etc.; interoffice correspondence (1961-1973) primarily between Holter and his secretary, Anna Johnson, and business manager, W.A. Munn; miscellaneous correspondence (1917-1946); court papers (1957, 1964); diaries (1924, 1942, 1945); financial records (1935-1975) including Holter's portfolio; laboratory records (1940) for Holter's laboratory in California; legal documents (1931-1982); press releases (1941-1964); printed material (1941-1983) arranged alphabetically by folder title; school notes and records (1927-1979) including many of Holter's course notes, exams, etc.; speeches and writings (1940-1983) arranged alphabetically by title (many speeches became published articles); subject files (1937-1984) arranged alphabetically by title (many titles given by Holter); miscellany (1937-1938); and clippings (1935-1982). Many times it was not possible to determine, particularly in correspondence, if the matter being discussed was concerned with Holter as the director of the Holter Research Foundation or as a scientist and business man separate from the foundation. Holter's interests were quite varied and this is reflected in the number and nature of the subject files he created and maintained. Similarly, it is not always possible to know if Holter's interest and activity in certain associations and groups and his appointments to various positions were related to the foundation or simply to Holter. The researcher should be advised to look at both subgroups when interested in a scientific topic. In addition, it should also be noted that some of Holter's speeches and writings were kept as subject files which include research materials, correspondence, etc.

The Norman J. Holter/U.S. Navy Subgroup reflects Holter's work on atomic bombs and wave reaction during and after World War II. This subgroup includes general correspondence (1942-1947); outgoing correspondence (1946) composed of Holter's letters to his family during Operation Crossroads at Bikini Atoll; interoffice correspondence (1941-1947) between staff members of the expedition; diaries (1943-1946) kept by Holter detailing his work for the Navy; financial records (1942, 1946); press releases for Operation Crossroads; printed material (1946-1947); reports (1941-1946) including those written by Holter; subject files (1941-1946); miscellany (1941-1947); and clippings (1946).

The Norman J. Holter/University of California San Diego Subgroup primarilv contains materials documenting the work done by Holter while assistant chancellor. Included in the subgroup are general correspondence (1964-1966) arranged chronologically; interoffice correspondence (1964-1966) between Holter and other members of the university's administration arranged chronologically; press releases (1965-1966); printed material (1963-1969); subject files (1961-1980) arranged alphabetically by title (many titles given by Holter); miscellany (1964-1967); and clippings (1953-1967).

The Society of Nuclear Medicine Subgroup contains general correspondence (1954-1979) arranged chronologically; financial records (1954-1972); minutes (1954-1979); organizational materials (1954-1983); printed material (1954-1982); reports (1957-1979); speeches (1957-1979) including those by N.J. Holter; miscellany (1954-1983) including programs of annual meetings, etc.; and clippings (1954-1969). The material in this subgroup is most complete for the early years when Holter was active in the organization. Correspondents in this subgroup include Asa Seeds, Marshall Brucer, Milo Harris, Tom Carlisle, and Thrift G. Hanks.

The Montronics Inc. Subgroup contains general correspondence (1959-1963); financial records (1957-1960; legal documents (1960-1961); organizational records (1960); and miscellany (1961-1962).

The Mountain States Telephone and Telegraph Company Subgroup contains general correspondence (1955-1968); financial records (1945-1956); legal documents (1959); organizational records (1956-1965); printed material (1955, 1961-1966); reports (1954-1963); subject files (1964); miscellany (undated); and clippings (1955-1961).