Researchers who find mention of the Confederate prison, Andersonville, in their ancestor’s Compiled Military Service Record (CMSR) or pension file should be interested in taking the next logical step in their research.
Andersonville prison records that were microfilmed as National Archives Microfilm Publication 1303, Selected Records of the War Department Commissary General of Prisoners Relating to Federal Prisoners of War Confined at Andersonville, Georgia, 1864-65, and can be found digitized online at FamilySearch.org at https://familysearch.org/search/collection/2019835, as well as at Ancestry.com.
In addition, it’s worth checking the “Claims Made for Money Taken from Federal Prisoners of War Confined in Confederate Prisons, 1866–1867,” https://catalog.archives.gov/id/615449, to see if the ancestor filed a claim. There is only a small possibility of this, because the opportunity to make a claim was not well known. My article about these records – “The Rebs Took My Money!” – is online here: https://twelvekey.files.wordpress.com/2015/03/ngsmagazine2015-04.pdf.
William Marvel’s book, Andersonville: The Last Depot, is an excellent book on life at Andersonville, and solidly grounded in archival research.