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

Parasitic worms (also known as helminths) can cause a variety of 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 (Centers for Disease Control and Prevention 2013). Experts disagree about whether the health effects of parasitic worms are relatively minor or quite severe (Taylor-Robinson et al. 2019; Croke et al. 2016).

Parasitic worm infections can be treated through mass drug administration (GiveWell 2013). 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 some evidence that reducing worm loads among children results in substantial increases in future earnings (Hicks, Kremer & Miguel 2015), though some have challenged these findings (Humphreys 2015; Jullien, Sinclair & Garner 2016).

Due to the low cost and the probability that it will increase future earnings, GiveWell regards mass drug administration as a priority program (GiveWell 2009) and rates donating to deworming charities as having high expected value (Conley 2016). Two of GiveWell's top recommended charities, Deworm the World Initiative and SCI Foundation, focus on deworming through mass drug administration.