There have been a number of documented cases in which governments, militaries, intelligence agencies, prisons, hospitals, universities, or corporations conducted human experiments without informed consent or through coercion. Some are well documented and officially acknowledged; others remain partially disputed or incompletely documented.

Here's a chronological overview of some of the most significant cases.

Years	Incident	What happened
1932–1972	Tuskegee Syphilis Study	Hundreds of Black men with syphilis were deliberately left untreated so researchers could observe the disease, even after penicillin became available.
1939–1945	Nazi Human Experimentation	Prisoners in concentration camps were subjected to freezing, infectious disease, sterilization, poison, and surgical experiments without consent.
1932–1945	Unit 731	Conducted vivisections, biological weapons testing, frostbite studies, and plague experiments on prisoners in occupied China.
1946–1948	Guatemala Syphilis Experiments	U.S. researchers intentionally infected prisoners, soldiers, and psychiatric patients with sexually transmitted diseases without consent.
1940s–1950s	Stateville Penitentiary Malaria Study	Prisoners were deliberately infected with malaria to test antimalarial drugs. Although volunteers were used, questions remain about coercion.
1940s–1970s	Radiation Experiments on Humans	Numerous U.S. government-funded studies exposed hospital patients, soldiers, pregnant women, and children to radiation without adequate informed consent.
1950–1953	Operation Sea-Spray	The Navy released bacteria over San Francisco to study biological warfare dispersion. Residents were unaware.
1953–1973	Project MKUltra	The CIA funded hundreds of experiments involving LSD, hypnosis, sensory deprivation, and psychological manipulation, often without subjects' knowledge.
1955–1975	Holmesburg Prison Experiments	Inmates underwent pharmaceutical, cosmetic, and chemical testing under conditions criticized as coercive.
1956–1970s	Willowbrook State School Hepatitis Studies	Children with intellectual disabilities were intentionally infected with hepatitis to study disease progression and vaccines.
1963	Jewish Chronic Disease Hospital Study	Elderly hospital patients were injected with live cancer cells without being fully informed.
1960s	Human Testicular Irradiation Experiments	Prisoners and institutionalized patients had reproductive organs exposed to radiation, often with questionable consent.
1960s–1970s	Oregon and Washington Prison Drug Studies	Pharmaceutical companies tested drugs on prisoners, raising concerns about informed consent.

Other notable examples

U.S. military and intelligence

• Edgewood Arsenal Human Experiments (1955–1975)
  • Thousands of soldiers were exposed to nerve agents, LSD, incapacitating drugs, and chemical weapons.
  • Many volunteers were not fully informed about the risks.
• Operation Whitecoat (1954–1973)
  • Volunteer Seventh-day Adventist soldiers were exposed to infectious diseases.
  • Generally regarded as having better consent procedures than many contemporary studies, though still ethically debated.

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Radiation experiments

Examples include:

• Feeding radioactive iron and calcium to children at the Fernald State School.
• Injecting plutonium into unsuspecting hospital patients.
• Exposing military personnel to nuclear blast effects during Cold War weapons tests.

Many of these were investigated by the Advisory Committee on Human Radiation Experiments in the 1990s.

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Biological warfare testing on civilians

Besides Operation Sea-Spray:

• Operation LAC (1957)
  • Zinc cadmium sulfide particles were dispersed over large parts of the United States to study airborne spread.
• New York City Subway Biological Test (1966)
  • Harmless bacteria were released in the subway system to study how biological agents might spread.

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Institutionalized children and vulnerable populations

• Monster Study (1939)
  • Orphaned children were subjected to psychological experiments intended to induce stuttering.
• Milgram Experiment (1961)
  • Participants believed they were administering painful electric shocks. While not covert in the same sense, the study relied heavily on deception and became a landmark in research ethics.
• Stanford Prison Experiment (1971)
  • Volunteers experienced severe psychological distress during a simulated prison experiment that lacked adequate oversight.

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Outside the United States

Examples include:

• Canadian MKUltra Experiments
  • Patients at the Allan Memorial Institute underwent drug administration, electroshock, sensory deprivation, and "psychic driving" without meaningful informed consent.
• Apartheid-era Chemical and Biological Warfare Programme (Project Coast)
  • Included research into chemical and biological agents under the direction of Wouter Basson.
• Soviet Psychiatric Abuse
  • Dissidents were involuntarily hospitalized and subjected to psychiatric treatments as a form of political repression.

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Common ethical violations

Across these cases, several recurring themes emerge:

• Lack of informed consent
• Deliberate deception
• Exploitation of vulnerable groups (prisoners, children, racial minorities, psychiatric patients)
• Withholding effective treatment
• Exposure to serious or unknown risks
• Poor or nonexistent independent oversight
• Failure to allow participants to withdraw

Many of these incidents directly influenced modern research ethics, including the Nuremberg Trials' resulting Nuremberg Code, the Declaration of Helsinki, and the Belmont Report, which established principles such as respect for persons, beneficence, and justice that continue to govern human-subject research today.