BACKGROUND: Diarrhoea and soil-transmitted helminth (STH) infections represent a large disease burden worldwide, particularly in low-income countries. As the aetiological agents associated with diarrhoea and STHs are transmitted through faeces, the safe containment and management of human excreta has the potential to reduce exposure and disease. Child faeces may be an important source of exposure even among households with improved sanitation. OBJECTIVES: To assess the effectiveness of interventions to improve the disposal of child faeces for preventing diarrhoea and STH infections. SEARCH METHODS: We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, and 10 other databases. We also searched relevant conference proceedings, contacted researchers, searched websites for organizations, and checked references from identified studies. The date of last search was 27 September 2018. SELECTION CRITERIA: We included randomized controlled trials (RCTs) and non-randomized controlled studies (NRS) that compared interventions aiming to improve the disposal of faeces of children aged below five years in order to decrease direct or indirect human contact with such faeces with no intervention or a different intervention in children and adults. DATA COLLECTION AND ANALYSIS: Two review authors selected eligible studies, extracted data, and assessed the risk of bias. We used meta-analyses to estimate pooled measures of effect where appropriate, or described the study results narratively. We assessed the certainty of the evidence using the GRADE approach. MAIN RESULTS: Sixty-three studies covering more than 222,800 participants met the inclusion criteria. Twenty-two studies were cluster RCTs, four were controlled before-and-after studies (CBA), and 37 were NRS (27 case-control studies (one that included seven study sites), three controlled cohort studies, and seven controlled cross-sectional studies). Most study sites (56/69) were in low- or lower middle-income settings. Among studies using experimental study designs, most interventions included child faeces disposal messages along with other health education messages or other water, sanitation, and hygiene (WASH) hardware and software components. Among observational studies, the main risk factors relevant to this review were safe disposal of faeces in the latrine or defecation of children under five years of age in a latrine.Education and hygiene promotion interventions, including child faeces disposal messages (no hardware provision)Four RCTs found that diarrhoea incidence was lower, reducing the risk by an estimated 30% in children under six years old (rate ratio 0.71, 95% confidence interval (CI) 0.59 to 0.86; 2 trials, low-certainty evidence). Diarrhoea prevalence measured in two other RCTs in children under five years of age was lower, but evidence was low-certainty (risk ratio (RR) 0.93, 95% CI 0.84 to 1.04; low-certainty evidence).Two controlled cohort studies that evaluated such an intervention in Bangladesh did not detect a difference on diarrhoea prevalence (RR 0.91, 95% CI 0.64 to 1.28; very low-certainty evidence). Two controlled cross-sectional studies that evaluated the Health Extension Package in Ethiopia were associated with a lower two-week diarrhoea prevalence in 'model' households than in 'non-model households' (odds ratio (OR) 0.26, 95% CI 0.16 to 0.42; very low-certainty evidence).Programmes to end open defecation by all (termed community-led total sanitation (CLTS) interventions plus adaptations)Four RCTs measured diarrhoea prevalence and did not detect an effect in children under five years of age (RR 0.92, 95% CI 0.79 to 1.07; moderate-certainty evidence). The analysis of two trials did not demonstrate an effect of the interventions on STH infection prevalence in children (pooled RR 1.03, 95% CI 0.64 to 1.65; low-certainty evidence).One controlled cross-sectional study compared the prevalence of STH infection in open defecation-free (ODF) villages that had received a CLTS intervention with control villages and reported a higher level of STH infection in the intervention villages (RR 2.51, 95% CI 1.74 to 3.62; very low-certainty evidence).Sanitation hardware and behaviour change interventions, that included child faeces disposal hardware and messagingTwo RCTs had mixed results, with no overall effect on diarrhoea prevalence demonstrated in the pooled analysis (RR 0.79, 95% CI 0.49 to 1.26; very low-certainty evidence).WASH hardware and education/behaviour change interventionsOne RCT did not demonstrate an effect on diarrhoea prevalence (RR 1.15, 95% CI 0.93 to 1.41; very low-certainty evidence).Two CBAs reported that the intervention reduced diarrhoea incidence by about a quarter in children under five years of age, but evidence was very low-certainty (rate ratio 0.77, 95% CI 0.71 to 0.84). Another CBA reported that the intervention reduced the prevalence of STH in an intervention village compared to a control village, again with GRADE assessed at very low-certainty (OR 0.17, 95% CI 0.02 to 0.73).Case-control studiesPooled results from case-control studies that presented data for child faeces disposal indicated that disposal of faeces in the latrine was associated with lower odds of diarrhoea among all ages (OR 0.73, 95% CI: 0.62 to 0.85; 23 comparisons; very low-certainty evidence). Pooled results from case-control studies that presented data for children defecating in the latrine indicated that children using the latrine was associated with lower odds of diarrhoea in all ages (OR 0.54, 95% CI 0.33 to 0.90; 7 studies; very low-certainty evidence). AUTHORS' CONCLUSIONS: Evidence suggests that the safe disposal of child faeces may be effective in preventing diarrhoea. However, the evidence is limited and of low certainty. The limited research on STH infections provides only low and very-low certainty evidence around effects, which means there is currently no reliable evidence that interventions to improve safe disposal of child faeces are effective in preventing such STH infections.While child faeces may represent a source of exposure to young children, interventions generally only address it as part of a broader sanitation initiative. There is a need for RCTs and other rigorous studies to assess the effectiveness and sustainability of different hardware and software interventions to improve the safe disposal of faeces of children of different age groups.