Soldiers who have taken part in peacekeeping missions suffer high levels of mental health problems, post-traumatic stress disorder and alcohol abuse.
A study says the rate is far higher than for veterans of more recent missions and only slightly below that of Vietnam veterans.
Since 1945, Australia has contributed more than 34,000 troops to 23 major peacekeeping operations.
The study, commissioned by the Department of Veterans Affairs and conducted by the Australian Centre for Posttraumatic Mental Health, examined the mental and physical health of a more than 1000 veterans.
They had participated in seven missions including Rwanda (1994-95), Cambodia (1991-93), Somalia (1992-96) and East Timor (1999-2002).
They reported a high level of exposure to potentially traumatic events including death threats, witnessing misery and degradation, and seeing dead bodies.
"While around half of the participants appear to be coping well with little or no evidence of psychological dysfunction, around one quarter report moderate levels of mental ill-health and vulnerability, with slightly over one quarter ... reporting more severe diagnosable problems," it said.
Of particular concern was that 10 per cent reported thinking of suicide.
A separate study examined 680 veterans of the Rwanda mission, launched following the 1994 mass slaughter in which the country's Hutu ethnic group massacred as many as a million of their Tutsi neighbours.
All were exposed to high levels of trauma, notoriously the Kibeho massacre of April 1995 when 32 Australian soldiers witnessed the murder of some 4000 refugees by government troops.
The study specifically examined claims for veterans compensation, finding 31 per cent had claimed for PTSD, a rate significantly higher than for other missions.
Peak periods for compensation claims came five and 11 years after the mission ended.
The Rwanda deployment included a large group of medical personnel who reported much lower levels of PTSD than accompanying infantrymen and support personnel.