Soil-transmitted helminth (STH) infect an estimated 1.45 billion people worldwide, therefore remaining a global health problem. Deworming programmes are effective in reducing STH prevalence but rapid reinfection occurs in the absence of decreased environmental contamination. Therefore WASH interventions are obvious candidates for sustainable control. WASH for WORMS is a cluster-randomised controlled trial to quantify the impact of a community-based WASH intervention integrated with periodic mass distribution of albendazole on infections with STH and protozoa, compared to mass deworming alone. In this trial, initiated in 2012, all participating communities in Timor-Leste received mass deworming every 6 months (for 2 years) and half of them also received the WASH intervention. The WASH intervention was implemented by WaterAid, Australia and included promotion of household latrines (based on “Community Led Total sanitation”), improved access to water and hygiene promotion. Infection prevalence and intensity were measured by qPCR. At baseline, the prevalence of STH in the 24 villages was high, with 62.3% of the participants infected with Necator americanus. In the intervention arm, N. americanus decreased from 62.8% to 32.2% at the 1st follow-up (FU1), with a further decrease to 21.7% at the 2nd followup (FU2), one year after completion of the WASH intervention. In the control group, N. americanus decreased from 61.8% to 36.9% at FU1, reaching 20.5% at FU2. At this time point, 77.7% of households in the intervention arm had a latrine whereas in the control arm 20.5% of the houses had one. Participating villages were followed for an additional year, with data collection ending in April 2016. Results will be presented for the study end-points and discussed in the context of the uptake of the WASH intervention. This trial is the first reported RCT evaluating the impact of integrated WASH and deworming interventions on STH infection; and will provide essential evidence for optimizing integrated STH control programmes.