The objective of this study was to determine the prevalence of malnutrition and its risk factors in children aged 0-10 years attending outpatient clinics in Manaus, Amazonas, Brazil. A cross-sectional epidemiological study of a population of 347 children was conducted. Data concerning socio-economic levels and food consumption were obtained by interviewing the accompanying guardian of each child. Dietetic evaluation was conducted using a semi-quantitative food frequency questionnaire, and faecal samples were examined by optical microscopy. Anthropometric measurements were transformed into percentiles and z-scores, and nutritional status was evaluated by reference to National Center for Health Statistics (NCHS) and Centers for Disease Control (CDC) indicators. Factors associated with undernutrition were analysed using a random-effects logistic regression model. The overall prevalences of underweight, stunting and wasting were 18.1, 15.5 and 10.7%, respectively, with reference to CDC growth curves, and 14.3, 17.3 and 4.4%, respectively, with reference to NCHS growth curves. The overall prevalence of wasting was statistical higher according to the CDC reference than that estimated using the NCHS reference (P=0.02). The prevalence rate of intestinal parasites was 58.8%. Risk factors associated with malnutrition were: low educational level of guardian respondent (OR=4.55), energy intake <54.5 kcal/kg (OR=4.55), children in age group 6-10 years (OR=3.54), and attendance at outpatient clinic for paediatric visit (OR=2.71). In the studied population, malnutrition (stunting, underweight and wasting) and parasite infection still represent serious public health problems. The risk factors identified in the present study confirm the influence of socio-economic factors on the nutritional status of children.