Background. More than a third of the world’s population is infected with intestinal nematodes. A majority of these infections occur in children. Current control approaches emphasise treatment of school age children, and there is a lack of information on the effects of deworming preschool childrenSetting: Within the Integrated Child Development System (ICDS) infrastructure in urban Lucknow (UP), IndiaDesign: Open Labeled randomised trialHypothesis: Our study hypothesis was that albendazole administration six monthly, as a single 400 mg dose in syrup, by the existing health care delivery system would be a practicable way to achieve mass deworming of preschool children and this might result in an improvement in weight gain of preschool childrenIntervention One group will receive usual health care by the existing health care staff, which included six monthly administration of Vitamin A concentrate. The other group will receive, in addition, 400 mg of albendazole (Zentel, Smith Kline & Beecham) in 10 ml syrup form. Five such doses will be given at six monthly intervals for 2 years.Main objective: To assess the impact of 6 monthly deworming on weight and height gain at the end of 2 years in children aged 1 to 5 years of age Main outcomes measures: Weight gain in 2 yearsInclusion criteria: Children 1 to 5 years, whose guardians give written informed consent. Exclusion criteria: Those not consentingSample size: Sample size was calculated for a continuous outcome. For a standardized effect size of 0.1, with a power of 80% and an alpha level of 0.05, using a 2-tailed t test, taking into account design effect, about 2000 children will be included in each arm.