Background. Organophosphorus pesticide (OP) self-poisoning is a major problem in the developing rural world. There is little clinical trial data to guide therapy, hindering the identification of best therapy. Despite the recognition of adverse effects, gastric lavage is commonly done in Asia. We aimed to identify studies assessing its effectiveness. Method. We systematically searched the literature for controlled clinical studies that assessed the effect of gastric lavage in OP pesticide self-poisoning. Results. All 56 studies identified were Chinese and reported benefit from the intervention studied, including multiple gastric lavages, use of norepinephrine or pralidoxime in the lavage fluid, concurrent treatment with naloxone or scopolamine, insertion of the gastric tube via a laparotomy incision, and lavage later than 12 h post-ingestion. However, only 23 were RCTs and none presented adequate methodology for their quality to be assessed. The patient population and study treatment protocol were not defined - large variation in case fatality in the control arm of the studies (from 4.5 to 93%) suggests marked variation between studies and likely between study arms. No study compared an intervention against a control group receiving no gastric lavage or provided any data to indicate whether a significant quantity of poison was removed. Conclusion. Despite widespread use of multiple gastric lavages for OP pesticide poisoning across Asia, there is currently no high-quality evidence to support its clinical effectiveness. There is a need for studies to identify in which patients and for what duration gastric lavage is able to remove significant quantities of poison. Following these studies, large clinical trials will be required to address the effectiveness and safety of gastric lavage (either single or multiple) in acute OP pesticide poisoning.