The international community has been criticised for not doing enough to locate those missing worldwide as a result of conflicts and other violence.
The report by the International Committee of the Red Cross highlighted what it called a hidden tragedy.
It called on those responsible for detaining civilians to allow families to obtain information about their loved ones' condition and whereabouts.
The ICRC report coincides with the International Day of the Disappeared.
There is no exact figure for the number of missing worldwide. In Iraq, official estimates put the number of missing in conflicts since 1980 at between 375,000 and one million.
There are still more than 17,000 people missing from the wars that tore apart the former Yugoslavia more than 10 years ago, the ICRC said in a statement.
Tens of thousands of people are also unaccounted for across Africa. The ICRC said about 22,000 people have been declared missing in Angola alone.
ICRC director of operations, Pierre Kraehenbuhl, said the suffering for families was immense.
"We have a figure from the morgue in Baghdad, 22,000 bodies have been brought to that morgue since early 2006. Half of those are unidentified.
"Multiply that by the number of relatives that remain without any news - you have an idea of how many people are there day-to-day facing the uncertainty of these disappearances."
Without confirmation that relatives are dead, families can live years in poverty with no access to pensions and no right to sell property.
The ICRC said that under international law, people should not go missing - deaths in battle should be recorded, detainees registered and families informed.
Mr Kraehenbuehl also insisted that political prisoners had the right to humane treatment, including contact with their families.