Deworming is the administration of anthelmintic drugs to treat humans afflicted with parasitic worms.

Parasitic worms (also known as helminths) can cause various health conditions and symptoms of varying severity. The most common parasitic worm infection, ascariasis, is estimated to affect 800 million to 1.1 billion people.^[1] Experts disagree about whether the health effects of parasitic worms are relatively minor or quite severe.^[2][3]

Parasitic worm infections can be treated through mass drug administration.^[4] This method of deworming has low costs and a high level of success in reducing worm loads (though reinfection can be rapid). There is also evidence that reducing worm loads among children substantially increases future earnings,^[5] though some have challenged these findings.^[6][7]

Due to the low cost and the probability that it will increase future earnings, GiveWell regards mass drug administration as a priority program^[8] and rates donating to deworming charities as having high expected value.^[9] Two of GiveWell's top recommended charities, Deworm the World Initiative and SCI Foundation, focus on deworming through mass drug administration.