Child malnutrition, including wasting, underweight and stunting, is associated with infections, poor nutrient intake, and environmental and sociodemographic factors. Preschool-age children are especially vulnerable due to their high growth requirements. To target interventions for preschoolage children in a community of extreme poverty in Peru, we conducted a household survey between October 2005 and January 2006 to determine the prevalence of malnutrition and its risk factors. Of 252 children <5 years old, the prevalence of wasting, underweight and stunting was 26.6, 28.6 and 32.1 %, respectively, based on the new WHO Child Growth Standards. Risk factors for wasting were: (1) moderate-high intensity Trichuris infection (OR 2.50; 95% CI 1.06, 5.93); (2) hookworm infection (OR 6.67; 95% CI 1.08, 41.05); (3) age (OR6-month 1.27; 95% CI 1.11, 1.46); (4) maternal education (secondary incomplete) (OR 5.77; 95% CI 2.38, 13.99); and (5) decreasing maternal BMI (OR1kg/m2 1.12; 95% CI 1.02, 1.23). Risk factors for underweight were: (1) moderate-high intensity Trichuris infection (OR 4.74; 95% CI 1.99, 11.32); (2) age (OR6-month 1.22; 95% CI 1.07, 1.38); (3) maternal education (secondary incomplete) (OR 2.92; 95% CI 1.40, 6.12); and (4) decreasing maternal BMI (OR1kg/m2 1.11; 95% CI 1.02, 1.21). Risk factors for stunting were: (1) age (OR6-month 1.14; 95% CI 1.02, 1.27) and (2) decreasing maternal height (OR1cm 1.12; 95% CI 1.06, 1.20). Overall, risk factors for malnutrition included both child and maternal determinants. Based on these data, locally appropriate and cost-effective dietary, de-worming and educational programmes should be targeted to mothers and preschool-age children. © The Authors 2007.