BACKGROUND: This updated Cochrane Review of reminiscence therapy (RT) for dementia was first published in 1998, and last updated in 2005. RT involves the discussion of memories and past experiences with other people using tangible prompts such as photographs or music to evoke memories and stimulate conversation. RT is implemented widely in a range of settings using a variety of formats. OBJECTIVES: To assess the effects of RT on people living with dementia and their carers, taking into account differences in its implementation, including setting (care home, community) and modality (group, individual). SEARCH METHODS: We searched ALOIS (the Cochrane Dementia and Cognitive Improvement Group's Specialized Register) on 6 April 2017 using the search term 'reminiscence.' SELECTION CRITERIA: We included all randomised controlled trials of RT for dementia in which the duration of the intervention was at least four weeks (or six sessions) and that had a 'no treatment' or passive control group. Outcomes of interest were quality of life (QoL), cognition, communication, behaviour, mood and carer outcomes. DATA COLLECTION AND ANALYSIS: Two authors (LOP and EF) independently extracted data and assessed risk of bias. Where necessary, we contacted study authors for additional information. We pooled data from all sufficiently similar studies reporting on each outcome. We undertook subgroup analysis by setting (community versus care home) and by modality (individual versus group). We used GRADE methods to assess the overall quality of evidence for each outcome. MAIN RESULTS: We included 22 studies involving 1972 people with dementia. Meta-analyses included data from 16 studies (1749 participants). Apart from six studies with risk of selection bias, the overall risk of bias in the studies was low.Overall, moderate quality evidence indicated RT did not have an important effect on QoL immediately after the intervention period compared with no treatment (standardised mean difference (SMD) 0.11, 95% confidence interval (CI) -0.12 to 0.33; I = 59%; 8 studies; 1060 participants). Inconsistency between studies mainly related to the study setting. There was probably a slight benefit in favour of RT in care homes post-treatment (SMD 0.46, 95% CI 0.18 to 0.75; 3 studies; 193 participants), but little or no difference in QoL in community settings (867 participants from five studies).For cognitive measures, there was high quality evidence for a very small benefit, of doubtful clinical importance, associated with reminiscence at the end of treatment (SMD 0.11, 95% CI 0.00 to 0.23; 14 studies; 1219 participants), but little or no difference at longer-term follow-up. There was a probable slight improvement for individual reminiscence and for care homes when analysed separately, but little or no difference for community settings or for group studies. Nine studies included the widely used Mini-Mental State Examination (MMSE) as a cognitive measure, and, on this scale, there was high quality evidence for an improvement at the end of treatment (mean difference (MD) 1.87 points, 95% CI 0.54 to 3.20; 437 participants). There was a similar effect at longer-term follow-up, but the quality of evidence for this analysis was low (1.8 points, 95% CI -0.06 to 3.65).For communication measures, there may have been a benefit of RT at the end of treatment (SMD -0.51 points, 95% CI -0.97 to -0.05; I = 62%; negative scores indicated improvement; 6 studies; 249 participants), but there was inconsistency between studies, related to the RT modality. At follow-up, there was probably a slight benefit of RT (SMD -0.49 points, 95% CI -0.77 to -0.21; 4 studies; 204 participants). Effects were uncertain for individual RT, with very low quality evidence available. For reminiscence groups, evidence of moderate quality indicated a probable slight benefit immediately (SMD -0.39, 95% CI -0.71 to -0.06; 4 studies; 153 participants), and at later follow-up. Community participants probably benefited at end of treatment and follow-up. For care home participants, the results were inconsistent between studies and, while there may be an improvement at follow-up, at the end of treatment the evidence quality was very low and effects were uncertain.Other outcome domains examined for people with dementia included mood, functioning in daily activities, agitation/irritability and relationship quality. There were no clear effects in these domains. Individual reminiscence was probably associated with a slight benefit on depression scales, although its clinical importance was uncertain (SMD -0.41, 95% CI -0.76 to -0.06; 4 studies; 131 participants). We found no evidence of any harmful effects on people with dementia.We also looked at outcomes for carers, including stress, mood and quality of relationship with the person with dementia (from the carer's perspective). We found no evidence of effects on carers other than a potential adverse outcome related to carer anxiety at longer-term follow-up, based on two studies that had involved the carer jointly in reminiscence groups with people with dementia. The control group carers were probably slightly less anxious (MD 0.56 points, 95% CI -0.17 to 1.30; 464 participants), but this result is of uncertain clinical importance, and is also consistent with little or no effect. AUTHORS' CONCLUSIONS: The effects of reminiscence interventions are inconsistent, often small in size and can differ considerably across settings and modalities. RT has some positive effects on people with dementia in the domains of QoL, cognition, communication and mood. Care home studies show the widest range of benefits, including QoL, cognition and communication (at follow-up). Individual RT is associated with probable benefits for cognition and mood. Group RT and a community setting are associated with probable improvements in communication. The wide range of RT interventions across studies makes comparisons and evaluation of relative benefits difficult. Treatment protocols are not described in sufficient detail in many publications. There have been welcome improvements in the quality of research on RT since the previous version of this review, although there still remains a need for more randomised controlled trials following clear, detailed treatment protocols, especially allowing the effects of simple and integrative RT to be compared.