Background Aggression occurs frequently within health and social care settings. It can result in injury to patients and staff and can adversely affect staff performance and well-being. De-escalation is a widely used and recommended intervention for managing aggression, but the efficacy of the intervention as a whole and the specific techniques that comprise it are unclear. Objectives To assess the effects of de-escalation techniques for managing non-psychosis-induced aggression in adults in care settings, in both staff and service users. Search methods We searched CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL and 14 other databases in September 2017, plus three trials registers in October 2017. We also checked references, and contacted study authors and authorities in the field to identify additional published and unpublished studies. Selection criteria We included randomised controlled trials (RCTs) and quasi-RCTs comparing de-escalation techniques with standard practice or alternative techniques for managing aggressive behaviour in adult care settings. We excluded studies in which participants had psychosis. Data collection and analysis We used the standard methodological procedures expected by Cochrane. Main results This review includes just one cluster-randomised study of 306 older people with dementia and an average age of 86 years, conducted across 16 nursing homes in France. The study did not measure any of our primary or secondary outcomes but did measure behavioural change using three measurement scales: the Cohen-Mansfield Agitation Inventory (CMAI; 29-item scale), the Neuropsychiatric Inventory (NPI; 12-item scale), and the Observation Scale (OS; 25-item scale). For the CMAI, the study reports a Global score (29 items rated on a seven-point scale (1 = never occurs to 7 = occurs several times an hour) and summed to give a total score ranging from 29 to 203) and mean scores (evaluable items (rated on the same 7-point scale) divided by the theoretical total number of items) for the following four domains: Physically Non-Aggressive Behaviour, such as pacing (13 items); Verbally Non-Aggressive Behaviour, such as repetition (four items); Physically Aggressive Behaviour, such as hitting (nine items); and Verbally Aggressive Behaviour, such as swearing (three items). Four of the five CMAI scales improved in the intervention group (Global: change mean difference (MD) −5.69 points, 95% confidence interval (CI) −9.59 to −1.79; Physically Non-Aggressive: change MD −0.32 points, 95% CI −0.49 to −0.15; Verbally Non-Aggressive: change MD −0.44 points, 95% CI −0.69 to −0.19; and Verbally Aggressive: change MD −0.16 points, 95% CI −0.31 to −0.01). There was no difference in change scores on the Physically Aggressive scale (MD −0.08 points, 95% CI −0.37 to 0.21). Using GRADE guidelines, we rated the quality of this evidence as very low due to high risk of bias and indirectness of the outcome measures. There were no differences in NPI or OS change scores between groups by the end of the study. We also identified one ongoing study. Authors' conclusions The limited evidence means that uncertainty remains around the effectiveness of de-escalation and the relative efficacy of different techniques. High-quality research on the effectiveness of this intervention is therefore urgently needed.