In the context of this review, civil unrest is defined as disharmony, expressive dissatisfaction and/or disagreement between members of a community, which leads to a situation of competitive aggression that may find expression as disruption of organisation, conflicts, damage to property and injuries. Such a breakdown of harmonious relationships, which may result in property damage and human injuries that may be threatening to life, varies in magnitude from participation of a very few individuals up to the involvement of large crowds of people, which may evolve into a full-scale riot. It is the latter situation often involving demonstrators, opposing groups and law enforcement personnel that can result in multiple casualties and present a very significant challenge to the resources of local healthcare institutions. The causation of civil unrest incidents is multifactorial and has generic, specific and potentiating elements. With the current national and international societal, political and discriminatory problems, it is likely that civil unrest incidents on both small and large scales will continue to occur at a high and possibly increasing rate on a worldwide basis, and for these not infrequent incidents, the medical community should be in a state of informed preparation. The circumstances of civil unrest incidents are very variable with respect to causation, overall magnitude, frequency, timing, geographical location, numbers of persons involved, demographics of participants, influence of extremists, confrontation with opposing groups and control measures used by law enforcement agencies. Methods used by police and security forces for the control of civil unrest incidents, if advanced negotiations with organisers and verbal warnings have failed, fall basically into two categories: physical and chemical measures. Physical methods include restraint holds, truncheons, batons, mounted horses, projectiles (such as bean bags, plastic and rubber bullets), water cannons, tasers and (rarely) live ammunition. All of these physical measures are associated with pain and immobilisation, and there is a high potential for soft tissue and bone injuries. Some of the more severe physical methods, including plastic and rubber bullets, may cause lethal injuries. The basis for using chemicals in civil unrest incidents is that they cause distraction, transient harassment and incapacitation, temporary impairment of the conduct of coordinated tasks and cause a desire to vacate the area of unrest. Although screening smokes and malodors have sometimes been employed, the major group of chemicals used are peripheral chemosensory irritants (PCSIs), which reversibly interact with sensory nerve receptors in exposed skin and mucosal surfaces, resulting in the production of local uncomfortable sensations and associated reflexes. Major effects are on the eye, respiratory tract and (to a lesser degree) skin. Thus, the induced transient pain and discomfort in the eye, respiratory tract and skin, together with associated lacrimation, blepharospasm...