A two-year study in rural Kenya explored the effects of water quality, sanitation, handwashing and nutritional interventions on rates of intestinal worm and Giardia infections. The results indicated that water treatment alone was sufficient to cause an 18 percent reduction in roundworm (Ascaris lumbricoides) infection rates. Adding sanitation and handwashing increased reduction to 22 percent. The other parasitic infections examined did not have significant reductions from any of the interventions.