Tested 47 first-year primary school children at a mission school in rural Zaire for cognitive ability with the Kaufman Assessment Battery for Children (K-ABC) adopted to the language of Kituba. Within a day of this test, each child was evaluated for blood hemoglobin (Hgb) level and the presence of intestinal parasites. Half of the children received an iron supplement (20 mg Fe) for 30 days and those children positive for the intestinal parasites of ankylostome or ascaris were randomly selected to receive either a vermifuge treatment or placebo. All of the children were again evaluated medically and cognitively 4 weeks after the initiation of treatment. Using discriminant analysis, performance on the Mental Processing Composite of the K-ABC 1 month after treatment in combination with increases in blood Hgb resulted in the successful classification of 74% in terms whether a child had received both iron supplement and vermifuge treatment (p = .007). With respect to our home evaluation for each child, factors related to the nutritional and economic well-being of the home environment proved a reliable marker for Simultaneous Processing ability. However, the present findings also suggest that over the short-term, changes in blood Hgb that accompany both vermifuge and iron supplement treatment together can improve certain aspects of cognitive ability, perhaps by means of heightened attentional capacity.