Background: In most industrialized countries, drowning ranks second or third behind motor vehicles and fires as a cause of unintentional injury deaths to children under the age of 15. Death rates from drowning are highest in children less than five years old. Pool fencing is a passive environmental intervention designed to reduce unintended access to swimming pools and thus prevent drowning in the preschool age group. Because of the magnitude of the problem and the potential effectiveness of fencing we decided to evaluate the effect of pool fencing as a drowning prevention strategy for young children. Objectives: To determine if pool fencing prevents drowning in young children. Search strategy: We used Cochrane Collaboration search strategy of electronic databases, searched reference lists of past reviews and review articles, Cochrane International Register of RCT’s, studies from government agencies in the United States and Australia, and contacted colleagues from International Society for Child and Adolescent Injury Prevention, World Injury Network, and CDC funded Injury Control and Research Centers. Selection criteria: In order to be selected a study had to be designed to evaluate pool fencing in a defined population and provide relevant and interpretable data which objectively measured the risk of drowning or near drowning or provided rates of these outcomes in fenced and unfenced pools. The completed studies meeting selection criteria employed a case-control design. No randomized controlled studies have been identified. Data collection and analysis: Three published studies met selection criteria. Data were extracted by two reviewers using standard abstract form. Odds ratios with 95% CI, and incidence rates, were calculated for drowning and near-drowning. Attributable Risk percent (AR%) was calculated to report the reduction in drowning due to pool fencing. Main results: Case control studies which evaluate pool fencing interventions indicate that pool fencing significantly reduces the risk of drowning. Odds ratio for the risk of drowning or near drowning in a fenced pool compared to an unfenced pool is 0.27 95%CI (0.16, 0.47). Isolation fencing (enclosing pool only) is superior to perimeter fencing (enclosing property and pool) because perimeter fencing allows access to the pool area through the house. Odds ratio for the risk of drowning in a pool with isolation fencing compared to a pool with three sided fencing is 0.17 95%CI (0.07, 0.44). Reviewer’s conclusions: Pool fences should have a dynamic and secure gate and isolate (i.e., four-sided fencing) the pool from the house. Legislation should require isolation fencing with secure, self-latching gates for all pools, public, semi-public and private.