Treatment for childhood nocturnal enuresis emphasizes either a psychological or pharmacological approach. The enuresis alarm, in comparative studies, has emerged as the most effective psychological treatment. In this review we investigate both outcome rates and influential factors from recently published studies. Material and methods. A search of papers published between 1980 and 2002 in the English language involving at least 10 children in which the enuresis alarm was employed as a stand-alone intervention revealed 38 studies. Results. Heterogeneity in terms of inclusion and outcome parameters made comparison between studies problematic. The most frequently adopted definitions were “wet at least 3 times a week” in terms of severity at inclusion, “14 consecutive dry nights” as a success criterion and “> 1 wet night a week” as a relapse criterion. Success rates across all studies ranged from 30% to 87% and were influenced by the type of enuresis, the treatment duration and the success criteria adopted. In an homogenous subset of 20 studies, 65% success with alarm treatment was found. Further analysis revealed equivalence between different forms of alarm, pre- and within-treatment predictors of outcome and possible mode of action. Relapse rates (ranging between 4% and 55%) were reported in 20 studies, with an homogeneous subset indicating that 42% of children relapsed following alarm treatment. Conclusions. The enuresis alarm is an effective intervention for children with nocturnal enuresis. There are a number of factors, both pre- and within-treatment, that appear to influence its effectiveness and may assist clinical decisions concerning its appropriateness for any particular child.