Objective To compare a novel code-word alarm with a commercially available wireless alarm for treating enuresis. Setting A tertiary paediatric centre. Patients Children aged 6-18 with at least 3 wet nights per week in the previous 6 months referred by doctors. Outcomes Primary outcome: the proportion who achieved a full response (14 consecutive dry nights) by 16 weeks. Secondary outcomes: change in frequency of wetting, duration of alarm training, percentage of wet nights that the child woke to the alarm, adherence to treatment, adverse events and satisfaction with treatment. Results Of the 353 participants, 176 were assigned to the code-word alarm and 177 to control. At 16 weeks, 54% (95% CI 47% to 61%) in the experimental group and 47% (95% CI 40% to 55%) in the control group had achieved a full response (p=0.22), with 74% and 66%, respectively, attaining a 50% or more reduction in wetting frequency (p=0.14). The experimental group woke more often than the control group (median percentage of waking 88% vs 77%, p=0.003) and had a greater reduction in wet nights (median reduction of 10 vs 9 nights per fortnight). Fewer in the experimental group discontinued therapy before achieving a full response (27% vs 37% discontinued, p=0.04). There were no significant differences in relapse rates at 6 months, adverse events or satisfaction between the two alarms. Conclusions Although the code-word alarm increased waking, no difference in full response rates was demonstrated between the two alarms.