A randomized, placebo-controlled treatment trial was conducted among 546 anemic (hemoglobin concentration, 7-11 g/dL) children aged 2-36 months in an area with intense malaria transmission in western Kenya. All children used bednets and received a single dose of sulfadoxine-pyrimethamine (SP) on enrollment, followed by either intermittent preventive treatment (IPX) with SP at 4 and 8 weeks and daily iron for 12 weeks, daily iron and IPT with SP placebo, IPT and daily iron placebo, or daily iron placebo and IPX with SP placebo (double placebo). The mean hemoglobin concentration at 12 weeks, compared with that for the double-placebo group, was 1.14 g/dL (95% confidence interval CI, 0.82-1.47 g/dL) greater for the IPT + iron group, 0.79 g/dL (95% CI, 0.46-1.10 g/dL) greater for the iron group, and 0.17 g/dL (95% CI, -0.15-0.49 g/dL) greater for the IPT group. IPT reduced the incidence of malaria parasitemia and clinic visits, but iron did not. The combination of IPT and iron supplementation was most effective in the treatment of mild anemia. Although IPT prevented malaria, the hematological benefit it added to that of a single dose of SP and bednet use was modest.